Know the basics of what you are using:

Get the Grand Tour.

Know some basic troubleshooting procedures.

Quick Links

• Change your account password: X.5, X.4
  
• What version do you have?
• Force quit an application
• Find the warranty information
• Basic Security information
  

Finder

• What is it?
• Working with Files & Folders
• Learn the Desktop
• Know the Dock
• Understand the Menu Bar
  
• Typing in another language
  

Printing

• Setting up network printers
• Setting up USB printers
  

Apple Mail

• Account Settings
• Differences between Entourage, Apple Mail and Piratemail
  
• Set up Out of Office Replies
• Disabling Out of Office Replies
  

Safari

• Setting the default home page
• Setting the default web browser
• Customizing the Tool Bar
• Turning on/off the pop-up blocker
  

Networking

• Cisco Clean Access Agent for the Mac
  

XCode

Can be installed from the Mac OS cd/DVD or its free from the Apple's Developer Website.