1. Avoid giving unknown online users your phone Number and address
2. Don't specify your relationship with your close relation especially your siblings online
3. Avoid specifying the Location you are at any point in time
4. Don't add strangers to your friends list anyhow
5. Don't accept invitation to visit or be visited by strangers
6. Don't judge people by their profile picture. Some people use another person's picture
7. When you meet new people, read between the lines. The kind of pictures, wall post and posture on their wall says a lot about their personality
8. Reconnecting with an old time friend is good, however some might have changed in their attitude along the line. So, watch your back
9. Don't flaunt your wealth online. Not everyone is happy with you.
10. Lastly, let God guide your decisions.

Source: http://www.finemventures.com/blog/93-facebook-security-tips