A good lock on your door. The rest is practice. I tend to reread the current chapter to get back into it. I try and avoid rewriting until after I'm done with the first draft because there's not much point to rewriting until I know exactly what I need to change, which means knowing all the points along the line (the essential ones, anyway). As others have said, it's a trial-and-error process of finding the method that works best for you.
It does get marginally easier with practice.
