I spent two years at my local summer camp.
Besides what you can bring, just be open and take it all in. Those two summers truly are the best two summers of my life (so far). Meet new people, get to know the personalities behind the staff members that you've seen for years. While it is a job and those scouts are there for merit badges, remember to talk to them just like normal people. Have conversations with them, if you see them around camp say hi. Create memories for yourself with your new family, but it's a great feeling when the scouts attending camp take time between their sessions to come say hi because it means you're making an impact.
Also, don't stress. It's a great and very fulfilling job and the entire senior staff wants you to succeed and do well and are there if you need help. Camp staff teaches you some incredible skills.