"Guest" account in OSX?

Name says it all.  Long story short, when I'm not at my macbook, others can use it without my discretion.  How do I make an account, which I'll call "guest" or something, with limited permissions?  sorry if this is a dumb topic, but I'm new to OSX.

You ARE aware that you can have the screensaver require a password?

If you want to create a guest account then you create it the same way you would create any other account, then make sure it doesn't have admin privs and finally activate whatever "parental controls" for the account you feel necessary.

Log out if you are concerned?

>>2
>>3
He's asking how to let people use his computer, not how to prevent them.

>>1
Apple Menu > System Preferences > Accounts
Click the lock.
Click the '+' buttons and create the guest account yourself. Don't give it admin rights.
Then go to Security preferences (click show all before), check the 1st option to make the screensavr ask for a password, and auto-logout if you need it.
If you trust people to do the right thing (HINT: don't), you can also just use fast user switching (in the login options of the accounts preferences)