Drink lots of water, your first week will be in a classroom, when you get to the floor, you will struggle at first, but just learn from the other loaders or unloaders, after a week of doing the same thing over and over, it will get easier, If you have a question about something ask, work at a steady but safe pace, people wont look down on you unless you are not working, always on your phone. do your best and keep safe, and again drink lots of water, those trailers are like ovens sometimes.
oh also look at the sticky for new package handlers at the top of the page. lots of info there