Something which is worth considering, enquire with the band if it is a separate DJ, and not a band member or their grumpy and worn out roadie who will act as the DJ.
Ideally, you would like somebody coming on after the band with fresh legs and not a fatigued band member who will DJ through a laptop, while at the same time stripping down and loading the bands gear into the van - Looks terrible!
A dedicated DJ will have full sound, greater selection of songs to take requests from your guests and much better disco lighting.
Guests tend to get disappointed upon band members who make a bad job tring to DJ and therefore leave the wedding early as they are not getting the full disco experience.
However, there are bands such as Drive, who offer the Bride & Groom the option to book a dedicated DJ such as myself.
Don't be afraid to ask the band you book for your wedding about their DJ should they offer you one as it is your hard earned money! Wishing you a Great Day on your Big Day!