You could set up an Ethernet network as previously mentioned (and further described shortly), or you could make your other computer a hard drive using
Firewire Target Disk Mode.
Ethernet newtork: (credit to MacAddict)
From OS X to OS X computer.
(1) Start up both machines. Now, for both machines...:
(2) Go into System Preferences.
(3) Click the Sharing pane.
(4) Give a unique name to each computer.
(5) Click the Personal File Sharing box underneath the Services tab. (A series of visible processes will take place. Wait for them to finish.)
(6) Go to the Network Pane.
(7) In the Show menu, select Built-in Ethernet.
(8) Close the System Preference window.
Save all changes.
Plug in your ethernet CO cable.
On one computer, select the Finder. And go to the menu item:
Go > Connect To Server
If you do not see your other computer in the menu, confirm that you have followed each of these steps properly.