Flash Frame-By-Frame Animation: Detailed Animation Part I

Turn on Onion-Skinning, and then go to the last frame of your animation; you can just estimate how long your animation will be (I originally estimated 17 frames for mine, then pared it down to 9; 17 might have worked at 15 frames per second (television animation) or 30 frames per second (film animation), but at 12 fps for web 17 was too slow) and then adjust it later by just shifting your frames around, a luxury that wouldn't be so easy if you were drawing this by hand.

Rough-sketch your last position based on the shapes that you used to capture your starting position; these are your primary keyframes, as your starting and ending points. Now we have to worry about getting from point A to point B, and all the baby steps in between.