Once you've settled on an entertainment venue and signed a contract, make sure that they send or fax you a booking confirmation -- and then follow up again a week later, and then shortly before the event. You don't want human error to ruin your party.
Some entertainment venues can offer special packages to make your life easier. In many cases, they'll provide all the dishes, flatware, linen, tables, wait staff, food, and sometimes even the entertainment. Don't hesitate to ask about what they'll throw in for an extra fee.