I haven't posted here in a while, and I'm sorry for that. I miss it.
Anyways, for me, it's very simple: have a plan and stick too it.
There are authors like Stephan King and Bernard Cornwell (my personal favorite) who will advise writers to just sit down and write. This doesn't work for me, I'm not on their level. I need a plan of attack, and I need to start as small as possible. Central conflict, premise line, whatever you want to call it; begin tiny. Very very tiny, then build out. As long as you're moving from one small thing to the next small thing, bit by bit, you'll find yourself through it in no time.
My favorite story planning guide is John Truby's Anatomy of Story. It's fantastic for getting you to think much more deeply about your story, even if you don't use the specific steps. It's geared toward screenwriters but it's perfectly good for other mediums. Story is story. There are plenty of others.
The only thing I'll warn against is simplistic "N-Act" structures. The three-act structure is a construct meant for long plays, in order to give the audience a break. It has no actual use in story construction. It's way to vague to help you construct your story unless you're already one of those brilliant minds who can just flow, like King and Cornwell (and I'd bet even they end up simply using their first draft the same way we mere mortals use a well-planned outline).
EDIT: Also, prowritingaid.com is an awesome resource for editing. It covers a lot of the technical aspects of writing so you don't have to spend so much time hunting down problems and more time perfecting your prose.