You may want to prevent some of these things from happening at your reception, a lot of them are preference.
Know Thy Music!
When it comes to playing music at a wedding or event it comes down to quality and not quantity. Some DJs try to impress clients with their huge variety of music, but if you think about it, the DJ will only be able to play about 150 songs during your wedding reception. Make sure that he has got the latest and most appropriate music for your event! Rather have him play 150 songs that your guests would like to hear, than simply playing random songs from his "huge" music collection!
No Business Cards On Display!
Remember it's your wedding and you are the client - and the client is always right. DJs will usually put their business cards out on display to generate more future business. If you don't want the DJ to do this, kindly let him know. Sound Bytes will honor this request. Some DJs may also wish to advertise or promote other businesses/services on your wedding day. Make sure you inform the DJ if this will be allowed or not.