It depends on the gym. You might want to take a tour of the gym you’re joining before you commit, so that you can see what goes on there and what other people are doing. When you’re at the gym, you’ll want to be in comfortable clothes for exercising. You are likely to want a water bottle and an iPod, and a notebook or something similar if you’re doing weight training or want to keep a lot for some other reason. You may want to carry a towel around with you. Many gyms have bottles of disinfectant solution and either paper towels or cloth bar towels scattered around the gym, and it’s considered polite to wipe down a piece of equipment when you’re done using it. If that’s the case at your gym, you won’t need to carry a towel around unless you want to.