It's all about your privacy settings.
Log in to Facebook. Up on the top right (right beside your name and "Home" is an arrow - click that, then "Privacy Settings".
From here you are editing who sees what on your account.
Next, click on "Edit Settings", which is to the right of "Timeline and Tagging". I think what you're looking for is the fourth one down, titled "Who can see posts you've been tagged in on your timeline?" Set it to "Friends", or whoever you want.
There are also a lot of other privacy settings on this page. This page might be useful in learning more about privacy settings on facebook: http://www.facebook.com/about/sharing/