Pete Blackshaw and Max Kalehoff have put together a list of 10 principles for ad campaigns leveraging consumer generated content, which are, in short:

1. Connect The Program To Larger Business Goals
2. Keep It Authentic
3. Be Transparent
4. Encourage Advocacy
5. Empower Syndication
6. Tap The Long Tail
7. Capture The Moment
8. Be Consistent
9. Embrace Criticism And Deprecation
10. Move From Campaign To Platform

You can find details to each point either here or here.

I particularly liked the points about making sure that whatever you do fits into a wholistic strategy, as well as making sure that you take the possible long term effects into consideration. With all the hype around this topic, I sometimes fear this tends to be neglected…