It is difficult (at least in some states) to book or check into a hotel as a minor. I went around visiting colleges by myself at 17, and ran into problems. Sometimes the person at the front desk doesn't think to ask, other times they simply wouldn't let me check in. It is really an odd law. If it is an option, use the Home Alone tactic. Have your parents call and reserve the room, and specify that their son will be checking in.
usually not a problem unless you look like you're 12. Just don't try to stay anywhere really nice. Stick to your average 2-3 star hotel. Using a credit or debit card for payment will usually get you in regardless, since they can charge you for any and all damages.