Interesting topic.
for me, I get a basic idea and note it down (always carry a notebook with me when im out and about, and next to where I sleep, ideas happen any time of the day

)
I then write it on my whiteboard at home. If it's still funny/interesting to me after a few days I start work on it.
- scribble down a storyboard on paper with tiny thumbnails.
-sketch full storyboard scene to scene in Flash
- by then I have a script ready for voices
- find some voice actors/actresses and get recordings
- put the voices into flash and time out the frames to match the timing of the animation
- actually make the animation

- export it without sound and import into after effects
- add sound back in and make sure it's all synched, + add sound effects
- Export big fat file of doom
- shrink big fat file of doom using MPEG streamclip to turn it into a bitesize MP4
- Finally upload :3