Privacy has long been a thorny issue for Facebook: Three years ago, the social networking site unveiled its Beacon advertising project, which resulted in a class-action lawsuit. December's privacy changes aimed at encouraging users to share more information publicly evoked plenty of criticism. And this week at Facebook's f8 conference, Facebook announced even more changes that affect users' privacy.

Keeping track of Facebook's ongoing updates, upgrades and changes--and how they affect your privacy--can be confusing and frustrating. We've sorted through the new wrinkles for you. Here's a list of five essential privacy settings you should review now and tweak accordingly to ensure your information remains safe.

1. Facebook Privacy Settings: "Instant Personalization" and "Like" Buttons

What the "Like" button is: Facebook's big announcement this week from the f8 conference was the new "Like" button, which you'll start seeing on blogs and news sites across the Web. When you click the button on an external website, you authorize Facebook to publish your activity to your Facebook profile (which, in turn, will also be published to your friends' news feeds). Also, when your friends visit the external site, they will see that you've visited that site, too.

What "instant personalization" is: The second part to Facebook's announcements this week was it's announcement of "instant personalization" on partner sites, which (right now) include Pandora and Yelp. Without adjusting your privacy settings, when you visit these sites, they can pull in information from your Facebook account, which includes your name, profile picture, gender and connections (and any other information that you've made visible to the public). If you visit Pandora, for example, the site could also pull in your favorite music artists, create playlists accordingly, and then notify your Facebook friends.

[Want more Facebook tips and tricks? Check out, "Facebook Bible: Everything You Need to Know About Facebook.]

How to change the privacy settings: The answer to the first part is easy--if you don't want your online whereabouts known, don't click any "Like" buttons.

The second part is more complicated. Click the "Account" option on your Facebook toolbar, then choose "Privacy Settings" and select the "Applications and Websites" option. At the bottom, you'll see, "Instant Personalization." Click "Edit Setting," then uncheck the box on the bottom of the page.

Note that unchecking the box will be enough to prevent partner sites from viewing your public information on Facebook, but when your friends visit these sites, your public information can be shared through them. To prevent this, you need to block the individual applications.

Next, visit the Pandora app page and Yelp app page, and choose "Block Application" for both.

2. Facebook Privacy Settings: Application Settings

What it is: When you add Facebook applications to your profile, you agree to allow the application to access certain information in your profile. Sometimes this includes which friends can and can't view the application from your profile, and whether or not you give the application permission to post stories to your wall and your friends' news feeds.

[For more on Facebook apps, read: "4 Facebook Apps That Add Professionalism to Your Profile.]

How to change these privacy settings: Go to your "Privacy Settings" page and choose "Applications and Websites." Then, click the "Learn More" button next to "What you share." Follow the link at the bottom of the page that says, "You can view the full list of Applications you have authorized on this page."

Here, you can view which applications you are using, delete any you no longer use and edit the settings for each individual one.

3. Facebook Privacy Settings: What Your Friends Can Share About You

What it is: Sure, you may have painstakingly weeded through your privacy settings and think your information is secure, but much of your information can still be accessed through applications that your friends use.

For example, lets say your friend uses a greeting card application. This application can access the information you've made publicly available (such as your name, profile picture, gender, current city, networks, friend list and pages), unless you change your settings.

How to change this privacy setting: Go to your "Privacy Settings" page and choose "Applications and Websites." Then, click the "Edit Settings" button next to "What your friends can share about you." This page will show you all the options that your friends' applications can access. Check or uncheck them based on what you're willing to share.