I’m using Facebook, and found this useful post about privacy settings. In short:

1. Understand your friend lists
2. Remove yourself from Facebook search results
3. Remove yourself from Google
4. Avoid the infamous photo tag mistake
5. Protect your albums
6. Avoid the post-breakup Facebook effect
7. Control what information applications can access
8. Make contact information private
9. Avoid embarrassing wall posts
10. Keep friendships private

Of course, every user has its own privacy level settings. But, I think most of them are few good points to consider. See details about each setting.