Selling iMac - how to clear personal data off computer

Hi all! I plan to sell my iMac Intel desktop and purchase a MacBook instead. However, I want to avoid any personal details being left on the HD of my iMac. What should I delete on my iMac to ensure there is no way the new owner can obtain my private information? Should I format the computer (can you do that with OSX? I don't know as I am still an Apple novice!). Are there particular folders that need clearing to protect my privacy?

Thanks in advance!

Put in the install DVD and restart the machine while holding down the C key until the gear wheel starts turning. This will start the machine from the DVD.

One screen into the install process (on mine) you can access the menu across the top. Go into the Utilities, and when the window comes up, choose erase. Another window will allow you to erase the drive with one pass or more securely with seven, and more securely yet with 32.

After erasing, you could reinstall the system (maybe with false info — if you don't have a buyer yet — or stop before you input anything) so the thing will boot. If you use false info, tell the buyer to reinstall.