Hydrate, that is the biggest thing. If you go and you are not hydrated it will be difficult for the attendent to find your veins withouth them rolling. Also, try to avoid fatty foods a few days before you go, you will be surprised how much fat actually hangs out in your veins, its kind of neat to see but gross none the less. Finally bring reading material, it can take up to two hours for the whole process, so bring something to keep you busy. Hope that helps :-)
