A great list of what not to do on facebook. Here is a simplified list of the article's advice: 1. Post Illegal Activities 2. Bullying 3. Trash Your Teachers 4. Post Objectionable Content From School Computers or Networks 5. Post Confidential Information 6. Overly Specific Location Check-Ins 7. Lie/Cheat/Plagiarize 8. Threaten Violence 9. Ignore School-Specific Policies 10. Unprofessional Public Profiles
11. Never Rely on Privacy Settings 100% 12. Post Emotionally
It doesn't get more simple than this very short simple presentation. This is a very good start! If you want to learn more about this topic, you can find many resources about digital citizenship under "DML" in my tags. I used DML to stand for Digital Media Literacy. I have some other resources under "Participation" that may relate in many cases.
Boiling digital citizenship down for easy digestion (7 slides + an addendum with some research background).