To start of a vector animation their are some things you should consider . This how you want to do it in After effects .
this video from Summit 41 , http://www.mtmograph.com/motion/ explains it best :
So what you need is the Duik you can get it here ; http://duduf.net/?page_id=151
You can ask me for character designs ready to be animated in after effects , i wil send some for free !!
Do you have questions , i will be happy to help out !!
Animways , Have fun!!