Bring along any hard drives or flash drives / usb sticks, as well as iPods and other music players and cameras that you plugged in to your computer around the time of infection.
Take the computer to the Helpdesk (provide any details and notes).
Shut down the computer and unplug the ethernet cable.
Jot down anything odd that happened, or any step that you took that preceded the attack/infection, and that may have been risky (installing a program, receiving an instant message, facebook message/post/app, etc).
If an attack/infection is suspected: Save all work immediately.
(this is a very rough outline that's much longer than necessary)