How to Transfer Files from Older Macs
You can transfer your files from older Macs that have a FireWire port without much fuss. You need a FireWire cable. When you start up OS X for the first time, you’re asked “Do You Already Own a Mac?” If you say yes, OS X offers to “transfer your info from another Mac with a FireWire port.” The transfer can copy files, network settings, and user accounts — including preferences and e-mail documents.
If you’re way past the initial OS X startup, you can still transfer your files. Macs with FireWire start up in “FireWire disk mode” if you hold down the T key while rebooting. Then you can plug the FireWire cable into your new Mac, which should see the new machine as an external hard drive. Then run the Migration Assistant, found in the Utilities folder, and you get the transfer capabilities even later in the game. Or you can just copy everything over to your Documents folder and sort things out later.