When I animate I always have a finished sprite, first of all. You're going to spend hours filling in all that color over and over later, when you don't need to.
Generally I then pick out the key parts like hands, feet and the head, then erase everything (not erasing the initial frame, of course, that would be dumb) and move all this small bits without changing their appearance so that I have the motion done, then I fill everything in inbetween... it saves me the trouble of finishing frame 2 and having frame 3 not fit.
But then again, I don't have much idea how I animate, it usually just turns out well... I never imagined I'd be any good at animating in particular, people have just said I am.

Just don't animate lineart like Adam said, and make some sort of template so you don't have to scrap lots of work halfway.