Early Set-up is a must. The DJ should not be bringing in equipment after the guests have begun to arrive. Equipment should be a professional sound system, and the DJ should be using CDs or Digital Audio Tape sources of music. Tape Cassettes or vinyl records are NOT acceptable. Background music is excellent to create atmosphere prior to the arrival of the bridal party.
Dinner music is also a plus.
Be careful to avoid being Upsold. An extra charge for any of the aforementioned services needs to be addressed. Background music, proper dress and conduct, use of the microphone, special entrance music and introduction to the dance floor are all a part of a DJ's responsibility to the customer, and should not be charged additionally. Delegate someone to be in charge of possible extra time, and make sure to clear any overtime with the venue supervisor. Cheap DJs are usually just that.