- Neverending tweens Close your tweens properly or don't have one at all!
- Label your layers I'm guilty of this from time to time, but for the most part, I LABEL THEM. Please, it's much easier to find things in a 100+ layer file if you label.
- Name your symbols Don't let Flash automatically label them for you! Give them /meaningful names/!!! Try using /folders/ even, yes, Flash has folders for organization!
There are more, I just can't think of them right now, I'm tired as crap. I'll add as I remember...