Ok… Keeping things organized in Flash is essential because if you are making a complicated animation you need to keep things easy to maintain.
This is a simple example. It doesn’t contain a lot of frames or animation but to illustrate my point it should be enough. That’s me waving in the animation BTW :P.
My first suggestion to never animate directly on the main timeline. Sure we did it in the examples but that was a learning process. Always animate everything in symbols and place those on the timeline.
I use a separate symbol for heads, arms, legs and the body. That makes it easier to simply rotate and reuse the same frames in a symbol multiple times and if I catch a mistake in a drawing I can just edit the symbol and don’t have to redraw every single frame from scratch.
How you divide the character body is your own preference. It depends on the design and structure of your character or object.
Always give your symbols names so you can find them easier. Do the same with layers.
Defining actions in Flash can also save you a lot of time. If you want an action to repeat define the action to replay a specific segment of the animation instead of inserting a whole slew of now frames. Keep in mind it’s always better to have a separate layer with empty frames to write actions in. Again… It’s too keep things organized and tidy.
Another thing I would suggest is to get Keyframe Caddy. The caddy is used to import any symbol to its library. Then you can take individual frames of the symbol from the caddy and replace the symbol with just that one frame when needed. Initially it was used for lip-syncing but it can be used in a wide variety of way other than that. I sometimes use it to animate eyes, legs, arms, etc. Basically almost the entire animation if I am doing it frame by frame. It saves a lot of time.