With Facebook Timeline, it's much more important than ever to be vigilant about posts or photos in which we've been tagged -- and it's contingent on us also to investigate our past posts and pictures. You can't be sure when an unwelcome surprise or embarassment will find its way onto your timeline, for all to see. While you may not have paid much attention to your privacy settings in the past, it's now very important to think about ways you can change those settings on individual posts -- or your profile overall -- in order to make sure that your Timeline represents you in a way you're comfortable with.
Don't stress out too much about imagining what may suddenly show up: You already know what's there, and being embarrassed or panicky does no good. However, it's important to be realistic about what information you want out there for people to see: The Facebook profile is, for most of us, the primary source and central repository of our personal information online -- meaning that it's up to us to stay in control of it.
Think about it this way: Just as there are conversations you would have with your friends that you wouldn't want to have with a parent or employer, there are probably photos and updates that you'd like to share with friends on Facebook, but might not want everyone you're connected with to have access to. Remembering that you're the one in control may help you to stay on top of decisions about who gets to see what.