- Log off: Once you are done especially if your are using a shared computer.
- Password: Never disclose it to anyone. You never know what people can do when they are drunk..no kidding..
- Personal data: Never post it unless you want to boast yourself and then repent..
- Trust: Don't trust everyone.I am not saying anyone...
- Access: Don't forget that you can use different privacy features to restrict who's allowed to see or comment on your content.
- Inappropriate content: Never post and report abuse if you find it abusing.
Few more security tips are here