I would clean your computer. Meaning run system utilities to defrag or repair disk permissions or repair disk depending on your computer. Have adapters and cables. A good idea is to have a semi-large collection of the songs you plan on playing on your phone or backup ipod. Have a 1/8 to RCA cable so you can easily connect in case your computer crashes.
TURN OFF WIFI. I've never had any issues with this, but I also have it off regardless. Disable any programs in the background you won't be using, like iTunes or Microsoft word. If you have your own mixes, preferably 30min to an hour long, play those if your computer needs to reboot. That way the transitions are smooth and people still can enjoy non-stop partying.
Bring comfortable shoes since you will be standing a long time. Some podiums or decks are shorter or taller. This will affect the way you stand over your decks. Which in turn will affect your spine.