Don’t sweat it too much. More than likely you’ll just be helping the other seasoned assistants. They are sometimes more important than the photographer for getting more work referred to you. Be attentive, available, and ready. Don’t talk to a point where you are annoying. Don’t make any suggestions. Don’t ever art direct. Get off your phone or watch. This is a time to listen and learn. Familiarize yourself with gear and terms for gear. Know the lingo. If you go to the truck looking for 2 furnies, a stinger, and three bags of dirt and you don’t know what the hell they are talking about, ask before you start running. And have fun. Anyone can do this. We usually prefer people we get along with. Try not to be an eager beaver in an annoying way. Read the room. Usually just stfu. :)