Although some of the best ballrooms are to be found in nice hotels, you may discover that they don't allow any loud music, due to the ballroom's proximity to the hotel residents. Often, however, they will allow acoustic music, especially if it is subdued.
Often (but not always), you won't be allowed to bring your own alcohol into a rented ballroom. Be sure to check with your ballroom's management about local restrictions. If you'd like a cash bar, it's a good idea to notify the caterer well in advance so they can arrange any necessary licenses.
If you're hosting a particularly long event -- say, 6-8 hours or more -- check to see if the ballroom's management will provide a discount on the hourly rate. They may be willing to do so, especially if you're already paying a large fee; but then again, they may not. It never hurts to ask.
