People have suggested writing an outline and I agree, and I will also add on to that. I highly recommend writing not just the overall plot events as labels or points but actual chunks of writing and dialogue so you can reference both the event AND the tone/style later on. During this you can check to make sure your ending has the proper means from the start, and you can also identify more plot holes this way. This seems like a lot of work up front, and it is. But rather than spending less time to toss out early chapters 1- 3 for example, then hit gobs at a time of down-time, why not wait until it's all mapped out to start typing and get your momentum going early with plenty of pre-planned reference material to keep you rolling.
THAT and write every day! I swear by my routine I worked hard on forming. I have written ~30-45 minutes every evening since last fall. It adds up to about ~500 words a day which doesn't sound huge, but if you are going for 2k word chapters thats a chapter every 4 days. And best part is, because it's such a habit, it just starts to happen on its own. This of course includes time spent on revisions from day before, continuity cleanup, etc.
The stronger the routine you form, the less of a role distractions will play IMO.
