Since I'm in the middle of a first draft at the moment, I thought this would be an excellent topic for the week. I know many would-be authors (and even authors who've already written their own books) worry about the correct procedure for working on first drafts. Do you simply write as fast as you can and worry about it when it's time to edit, do you edit as you go, or do you do a mix of both? So I'm going to give you my answer in both short and long form.
The short answer is to write it however you're most comfortable. As long as it gets written, you've done it the correct way.
The long answer is the same, but I'd like to expand on it. Some writers can turn off their internal editor and simply pour words onto the page. This usually means the first draft will be done quicker, but the editing process will take longer. Others claim they can't move on if a page is not perfect. They must edit, edit again, and so on until they are happy enough with the work to continue with new words. This will undoubtedly lead to first drafts taking a much longer time, but editing, at least the copy editing stage, will be much shorter. And then you have the middle ground, where you think about the final product (word choices, tense, POV issues, plot devices, etc.) as you write. You're not simply pouring words onto the page, but you're not taking the time to fully edit, either. Some days the words will fly onto the page, and others you will struggle to get many at all (though, to be fair, this happens no matter how you choose to work on your draft).
So how do you know which way to work? Simple: try different ways to see what makes you most comfortable. A comfortable writer is a productive writer. If you hate your process, why continue doing it? Find a better way. Personally, I choose the middle ground. I can't just let the words fly and fix them later, but neither do I see the point in fixing up everything as I go. I often spend too much time sitting staring at my paper trying to come up with that perfect word or phrase, but if I catch myself doing this too often, I can simply put a good enough word for now down (I will often highlight or circle the word to know to fix it in edits) and continue with my draft. This gets me through a first draft quick enough, even if it's not as quick as possible. I find it makes my editing easier, though it is still a long process.
How about you? Which first draft process do you use? Have you tried other methods, or do you simply know this is for you? Are you happy with your method, or are you still searching? Feel free to share in the comments!