A recent Guy Kawasaki How to Change the World post linked to a 6 minute video by Lewis Howes on 8 ways to use social media. A quick summary:

1. Be yourself
2. Get active on at least Facebook Twitter and LinkedIn
3. Provide awesome content
4. Be smart with your time
5. Be consistent
6. Promote others
7. Connect face to face
8. Thank others

Lewis' video adds a lot more detail, so check it out.