I need to loan my Mac to a friend, but don't want him to be able to access my personal files. How can I let him use the machine, but not my content?
It’s probably best to keep friends from examining your personal files too closely, and the Mac operating system, OS X, makes this simple. All you need to do is create a new user account on the Mac and tell your friend the credentials to log into that account.
To create a new user account, start System Preferences, and then select to the Users and Groups option. You will need to unlock the settings so that you can make changes and then add a new user. Supply a password for the new user, and then you’re all ready to loan them your Mac.
Your friend will be able to log into the new account you created, but won't be able to access your personal files. When the new user attempts to do so, the computer will display a get a warning indicating that the files aren’t available for this user. There’s really nothing your friend can do without knowing your password and logging into your account to get into your content. It's very safe, and this mechanism provides a great way to share the computer with other users. (If you’re really paranoid, you might want to consider also encrypting your data, but that’s a topic for a separate tip.)