But if you're not careful when you first allow these apps access to your information, they'll likely post your activity to your wall and to your friends' News Feeds. You have a few options.
Below the app summary information you see when you first choose to download an app is this option: "Who can see activity from this app on Facebook." How you've set your default privacy settings--either public, friends or a custom setting-- will be the automatic setting for all your applications, unless you change it.
-After you've installed an app: If you're not sure what your app preferences are or if you want to adjust them, you can review them one by one from within your Privacy Settings page.
From the drop-down menu in the top-right of your screen, select "Privacy Settings" then choose "Edit Settings" next to "Apps and Websites." On the apps privacy page, click "Edit Settings" next to "Apps you use"--this will show you all the apps that you have downloaded as well as the privacy and permissions associated with them.
Here, you can remove the app if you no longer want it connected to your account. You can also preview what permissions the app has and remove certain ones (some are mandatory and cannot be removed).
The last option, "App activity privacy" will tell you who can see posts and activity from this app. If you don't want Facebook to share your activity, change this option to "Only Me."