I guess you can check if the flash head is able to swivel, rotate properly.
Check the recharge time. Check if the flash is able to be configured via camera or via flash itself.
Use flash for a couple of shots.
Bring your own batteries?
Thanks for the help guys. I tried shooting in Av with the flash, as I understand it the camera (450D) will not meter by taking the flash into account because it uses the flash to fill the background, is that correct? It seems to result in my pictures being overexposed, do I drop the exposure or is there a better way to shoot in Av with flash?