Use secure virtual memory to protect information stored in memory
An introduction into the Security Pane - Make your computer more security
How to Open the System Preferences in Mac OS X Leopard
IF you want to lock the computer, you can enable a menu bar icon allowing you to do so
Stop your computer from automatically logging in to an account
Disable the Apple Remote Control from having an effect on your computer
Enable the Security Vault - encrypt your personal data
Change the Master Password for the Security Vault
Turn off the File Vault
Have your computer log out after a specified time of inactivity
Password protect the System Preferences, stop people from changing setting without an Administrator account
Password protect your system using a password protected screen saver