Mac Tips Daily! #50 - Screensaver Passwords

In this window, you need to make sure the padlock is unlocked. If it isn't, simply click on it in the lower left corner, and then authenticate.

Put a check mark next to 'Require password to Wake this computer from sleep or screensaver'. Click on the Padlock to lock your preferences. You may want to check out your screensaver options and see if they are set at a reasonable time - I have mine set to 5 minutes on inactivity.