I have two. Don't burn your bridges is the first piece of advice, which I'm sure we've all heard that one. The second one is about loaning and borrowing equipment. If you borrow someone's equipment return it in better shape than you got it. That means making sure everything is fully charged, clean, neatly presented, and returned as quickly as possible. If you loan your equipment, have the person sign some type of form stating when they'll return it, just so there's no confusion later on.