(I hope you are happy with this, because this is a huge post on your thread to have to be unhappy about)
I'm sort of vague on what you actually want here - like, are you asking what is the entire process of forcing yourself to go from original idea to written words so that you can get some ideas of how to get yourself to do this? This seems to be what you're asking but then what it looks like you actually want is advice on how to write well.
I'd definitely agree with the "write a million words" thing, to start with, in any case. No matter how many writing guides you read, no matter how many ideas you have, the biggest thing you need is experience. People tend to get writing confused with something more clear-cut, like baking cookies, or building a bed. Sure, you need a bit of practice for those things, but as long as you follow the instructions, you'll do okay. Writing isn't the same as that. People can tell you where to put periods and capital letters, and they can even give you some stylistic advice, but you can't skip practicing. It's like drawing. Even if you read a million times to draw a circle for the head and then split it into four sections to figure out where the facial features go, you will still draw many off-center noses.
That said, the most important thing to do is to write every day - and you'll see many, many professional, published authors say this if you look around a bit, because this is a big thing. Even if you just write a hundred words a day (any less than this will probably just make you feel kind of silly, but you can go for it if you want), it helps you keep writing on your mind. I tend to feel best either doing a thousand words a day with no plan (this is enough less than NaNoWriMo that it isn't too crazy, and then you still have many words to feel good about later), or a hundred words a day and then use the extra time to plan out what I'm doing and to do a better job on the hundred words.
Quantity and quality are both pretty good things in the writing world, so pick whichever one you're going for and stick with it for a while. You can mix it up and do different counts, and you can even switch counts later, but whatever you do, stick with it for a bit. Doing x words a day for a single day, even if it's a lot of words, is not in the spirit of writing every day, and you will not get the same results even if you get the same words at the end. It's important to think about writing constantly, not just over the weekend.
Once you've got some words to look at, look at them. Pinpoint the parts that are good, and the parts that bother you, and consider them. You can generally tell which parts these are. The hard part is figuring out why you like or dislike them. It is not always easy to figure this out. Look at the bad parts and see if you can see what they have in common, though - are they all fight scenes? Talking scenes? Maybe they have repetitive sentence structure. Maybe you forgot that this character isn't supposed to be able to touch magic swords and it's really bothering you in all of these scenes. If you find one thing in common, this is the thing you need to work on! If you don't find anything in common, that's okay too. Just try writing those scenes a different way and see if you like them better then. I'm awful at fighting scenes. So I've been writing a lot of them lately.
When you get a thing that you're bad at writing and you don't know how to be good at it, this is when you can ask for help. Sometimes the only thing you can do is ask Google and there's a lot of really awful writing advice out there, but if you look you can get some key elements. For instance, some general fighting scene things are to use short, snappy sentences, repetition, and sharper vocabulary words. Sometimes all you need is a hint to help you move forward.
If you can, though, ask someone to look at it for you. Lots of people tend to say something like "nice" or "you want help? I found a neat writing guide the other day!" without realizing you don't really want either of those things, so be specific. If they're worried that they're not very good at critique, just have them tell you which parts they liked best or worse. Worse, in particular, is good to ask for, because if they're nice they'll want to justify it and their justifications might give you some leads as to why those parts are bad ("well, I don't like the opening paragraph, but I think that's just because I hate it when authors do x and y, so it's probably just me..."), and if they're mean they'll want to tell you all about what's wrong with it. Nice people can have trouble knowing what to say about the good parts besides that they're good, and mean people are disinclined to tell you what the good parts even are. (I say mean people and nice people here because I think you know what I mean - some people feel that "mean" critique is more helpful, and some people don't think that)
In short, write a lot, and figure out the things that you don't like reading so you can write them better.
As for the writing process - I think that's pretty similar for most people. But I'll outline it for you, because I think there are some key things here that people tend to forget about or dismiss.
The first part, or the starting point, is of course the idea itself. This is easy. You will have many, many ideas over the course of your life - over the course of a single day, even! You might not recognize most of these as ideas that could be in a story. Some people don't recognize any of their ideas as story ideas and think they were born without creativity. This is silly, because you'll hear those same people voicing some pretty excellent story ideas, and frequently, if you listen. You just have to get in the habit of perceiving all things as potential stories, because all of them are. That time you won a pizza at the fair? I would read about that. The monster under your bed from when you were little that you were just discussing with your friend? You could write so many stories from that concept. That cat outside who vanishes when you open the door? What is it doing there? Why does it like your house? You don't know, do you? Maybe it's time to find out. These are just some examples of "mundane" events from your day-to-day life. I'm not even going to touch all those things you come up with talking to your friends. There are so many things. (I know you're not looking for idea advice, be quiet, this is my transition)
Then you realize that you have an idea that you want to share with people, or with your notebook. Sometimes you will just think "I would read that", but other times you actually want to be the person to tell these stories, and that's where you can hit a wall. You have an idea. What do you do with it?
Well, the answer it pretty clear - sit down and write it. But there can be some steps before this! And writing it isn't always as easy as it looks.
So there are a few things that I like to do that I think are helpful in general. A major thing that really helps me with my writing it talking it through somehow. It doesn't matter who you talk about it to as long as they're at least a little bit receptive. It's nice if they'll talk back, but what you really need is a sounding board. If no one wants to listen to you ramble, get a journal! I really like going over my plot in my journal. I get skeptical every time, but then I sit down and explain to my imaginary audience what is going on and what my problem is, and after getting all the ideas down on paper (virtual paper), I always, always get, at worst, several new and intriguing pieces to work with. I am fairly certain that most (if not all) other people could get similar results! I don't see how you could not. Just, one thing to keep in mind is that you probably want to make it a private journal, so you're never afraid to talk about your story. Or at least, make your silly rambly entries private. If you're writing in public, there's always that small bit of doubt. There's no need to add any bit of doubt to something that's already so difficult. You can make it public if you want input and if you won't be sad if no one replies (people get spooked and think they can't help), but that's really more talking to people and less journaling. And don't bother summarizing anything - the more effort you put into writing those entries, the more you'll get out of them.
Making notes is also useful. I have trouble actually keeping notes, but they're important to keep. Even if you really love your characters, even if you think you'll remember everything about your story, there are things you will forget! Some of these things will be things you can remember if you give it some thought, but it's nice to have something to look over. Other details will vanish from your head forever. I tend to think of it like "I guess that detail wasn't meant to be in the story :c" but that doesn't make it much less sad when you forget something you didn't want to forget. Keep notes! I tend to keep those on my journal, too. A text file is just so impersonal. Notes can be in the style of "bob - sword" if you like, or alternatively, "So I have this character Bob, and since everyone in my story has to have a weapon, I gave him this sword..." I tend to prefer the latter, because regular style notes are weird and I like talking, but if a short style works for you, go for it! Going into more detail tends to help you go into even more detail, but sometimes you just want notes.
With your ideas cleared up, it's a lot easier to write. It can be really daunting to actually start writing something - or to continue a piece of writing when you don't know where to go next with it. Anything that makes the process a little less scary is worth doing.
Something else that can be important though is what you're using to write! Notebooks feel a lot different than word documents, and an E-mail feels different still. Something like E-mail or a journal is good if you like a less formal atmosphere, but writing to yourself like that can feel weird, too, and there isn't as much space for writing - this is a problem if your segments tend to be too long for the amount of space you're given. It's interesting as an experiment, though, if you're tired of more standard mediums. The pros of word documents are pretty clear; they're very editable and sendable, and they have spell check, and they're very clean and neat. The main pro, however - the ability to edit it at your leisure - is also its greatest downfall. Because you can edit it, you think you should edit it, and then you trap yourself. The no editing rule isn't just for NaNoWriMo. You should put the rule on your other writing, at varying levels, because stopping to think about how terrible your writing is only slows you down and decreases your morale. Edit a chapter when it's complete. Edit a story when it's complete. Whatever stopping point makes the most sense to you - but don't stop in the middle to change things, whether you're writing for quality or not. Occasionally you can get away with this, but almost all of the time, you will get stuck. Don't do that to yourself.
The other thing about Word documents is that they are intimidating. Look at that blank page! So white. You can do a little about this problem by adding some things like a chapter heading, and I tend to write "lorem ipsum" onto my document until I think of how to start off, but the page is still scary. Really the best thing to do is just start.
Notebooks are nice because they're so difficult to edit, and they're a lot more friendly, and you can take them with on your daily adventures. Being difficult to edit (you'll make a mess if you keep scratching out words! And I don't know about you, but I find erasers that actually erase things are pretty rare) makes it so that you can continue without fear. Well, maybe the fear that someone will look over your shoulder and think that you're doing a bad job. But that's what the rest of your arm is for. Also, hand-writing can be hard to read, especially when you're scribbling trying to reach your word count so you can get to bed, and so then you're a lot less inclined to go back over it and criticize yourself for now. The trouble with notebooks is that writing by hand is a lot more difficult than typing, though sometimes the slower pace can give you time to think it through a little more - and you can't show it to a lot of people because they're on the Internet and your notebook is not on the Internet. And typing up pages of things you wrote at odd hours of the night is difficult enough to make you really wonder if it's worth it. Try out a notebook, though! Get a nice pencil (this is key - if you smudge you will never be able to read it) and see how it goes. Just don't ever crumple it up. Nothing should be crumpled, terrible or not. Keep it! It might look better later. Or it might help you feel that you've improved at some point! I'm always sad if I don't have archives because I tossed something, and I think lots of other people are sad about this, in retrospect. You can't un-destroy. If it seems bad, just stick it in a drawer or on a dusty bookshelf for a while. I'm also fond of writing notes and drawing pictures in the margins. Both of these can make you feel more like writing.
When you've got all that figured out, sit down and write! It's most useful, again, to give yourself goals to reach. Word count goals are best, although people will use chapter goals, page goals, and even a goal like "finish the whole thing." I don't like chapter goals because a chapter can be a single word or several dozen pages, so sometimes you'll have days where you don't do much and some days you won't be able to complete the goal. Page goals aren't too bad, but they're flexible - a page can get cut off because you're skipping a lot of space to add another chapter, or you might write a lot less on that page or a lot more based on whether your characters are shooting one-liners back and forth or whether you're writing a long description of the scenery. Finish goals are nice for a set length of time (for instance, a month) because they can get you to work ahead, but it's hard to really know how long something will take you. Will you finish your novel at fifty thousand? A hundred thousand? Higher? Who knows? You probably don't. I would recommend word count goals until and unless you find out you really feel more comfortable with one of the others. Whichever one gets you the best and fastest writing is what you want to go with, and published authors will use any of those methods, but word count is a nice, clear goal to aim for, and this is important for a beginning writer in particular.
Then there's the writing itself. I asked and something you're apparently looking for is how people choose words. This isn't really a big deal, usually! Just write the first words that come to mind to describe the scenario, even if they're bad. Once you get that done, you can move forward. Remember, you can always go back and edit, but you can't retrieve the sad time lost staring at blank space! You can't edit a blank page! Writing anything increases morale and helps you to write better later. I'll use a thesaurus or ask someone for help if there's a word on the tip of my tongue, or if I know there's a better word in place of this one, otherwise, I leave it be. If I'm writing in my notebook, I'll occasionally strike through a word or phrase and write something else above it or next to it (I write single-spaced; my hand-writing is tiny, but it's still difficult to fit notes sometimes), and if it's a big thing like "okay so I decided Bob was wearing a giant alligator hat this whole time" then I'll just make a note of that and pretend a potential reader wouldn't be extremely confused. Otherwise, I leave my notebook alone. Word documents don't get any editing - if I move on to the next paragraph, the words before it are set in stone. I'll make occasional exceptions if it's a minor edit, or if I think of some piece that will help me write more a bit later, but I stick to the page I'm on, always. If something needs to be edited, it requires a whole other document. You might not need to be quite this extreme, but I think it helps - and I really like to preserve every way that my stories have been. It's a nice contrast, and it's really interesting to read old versions. Sometimes they're better than you remember!
Once you're started, don't let anything get you down. Breaks are okay, but when you get distracted, it's difficult to force yourself back into it, because writing is hard work. Keep your materials around you - keep Word documents open, and keep notebooks at your desk. If they're around a lot, you'll become accustomed to their presence and it won't be so much of a reminder anymore, but sometimes you will mouse over your tab bar or glance at the other side of your desk and think of something. Additionally, the harder you make it to access your writing, the less you will want to do it - and it's difficult enough as it is. I don't have trouble doing this with Word documents, and it helps, but my notebook is in a drawer I can only just barely get into, and it really detracts from the experience. Someday I will find it a new home.
Another general tip: study critique! Any kind of critique. Even art critique. It seems like art critique would only help you critique art, but it really helps you develop the skills to pinpoint features that you like and dislike - about anything! You will learn vocabulary for paintings, but you will learn skills for life. If you can tell what it is about your writing that's bothering you, it will be that much simpler to fix!
Also: Outlines. In theory, I am horribly skeptical of outlines, but in practice, they are very, very useful. I never liked writing outlines for English essays. They were short essays! I could form my plan in my head in a matter of seconds! This is not the case with stories - novels in particular. I think a lot of people who dislike outlining are imagining the wrong sort of outline here. "Outline" brings up images of letters and numbers and nested list items. "That's boring," you think. "Letters and numbers will stifle my creativity! Plus, you think I can stand to do that for an entire novel?"
This is not the outline we are looking for, and you certainly don't have to go for your entire novel at once. When I "outline" or rather, plan, I sit down at my journal (the journal again), explain what point I am stuck at and all the things that cannot happen next because of what's going on, and then I stay there until I have figured out enough of the rest of the story to go on for a few days (at least). This makes it a lot easier to just sit down and write, because even if you are writing badly (everyone spends some time writing badly), you know where you're going. Having a plan makes you feel great. You are organized. You can do things. And you waste a lot less time rambling about random things and more time really writing. Also, you have a little leeway for things like foreshadowing, and you'll have to do a lot less retcon to make everything fit.
This is all subjective, naturally, but I think all of this works pretty well as a general guideline of what sorts of things to do, especially if you're feeling like a confused beginning author.
Of course, the most important thing to do is believe in yourself! Believe in your stories! This is key. Whether you think you can, or you can't, you are right. For most things, anyway, and writing is definitely one of those things.
You can do it!
