Your Mac is full of settings that will help you configure it to better suit your needs. Just click System Preferences to get started.
Mac OS X has a great built-it search function called Spotlight that helps you find any file on your Mac. Never loose an email or a document again!
Guest logins is a convenient and secure way of letting friends (or strangers) use your Mac without letting them access your personal files.
So you've learned how to install applications on your Mac. Now for the hard part: uninstalling the applications that you don't need anymore.