After a day spent cleaning up my social media streams, a few lessons learned:
1. Do keep it short and sweet, unless you really have more to say. Word count and follower numbers are not correlated.
2. Don't let an account lie fallow. If you're not posting or getting traffic, delete it.
3. Do focus on what you're good at. I like telling stories, giving advice and commenting. Video, audio and online community gardening, not so much.
4. Do leverage your content across multiple streams. I like Posterous a lot for this.
5. Don't be afraid to try. Social media is for pioneers. Sometimes we chase fool's gold, but that's OK. Other times we discover voice tweeting. (Try Voice to Tweet for Droid and Dragon for iPhone, both free.)
Most importantly - have fun and good luck!