Don't expect to be able to find a banquet room for your needs at the last minute. Good banquet rooms are often booked solid months in advance. If you can, it's a good idea to book your room at least six months in advance; for events like wedding receptions, you might need a longer lead time.
When looking for a good banquet room, don't forget to check out your local hotels. Most offer banquet rooms and banquet halls for decent prices, and in most cases will provide the wait staff, food, extras, and everything else. Even smaller hotel chains may provide these services.