Things to remember when hiring a DJ...
It is important to remember that the DJ can make or break the success of your reception since that's the person who will control the flow of the evening. If your DJ is not an experienced professional there will be a great deal of room for mistakes and disappointment. You only get one chance to perfectly execute one of the most important nights of your life.
Make sure that the DJ understands that the wedding is your event and not his/her's. Your DJ should always listen to what you want and what your expectations are. Don't let a pushy DJ tell you what you will get, but rather tell them what you want. If you don't get a good vibe about them, go elsewhere immediately.
Never hire a DJ based on price alone. DJ's vary greatly in personality and style. It is most important to hire someone you can trust to show up, do a great job in following your wishes, be very organized in keeping you on your timeline and adding just the right amount of interaction to keep things fun. You will be spending several thousand dollars for everything else, don't get caught with a bad DJ and have guests leaving after dinner.
It is also important to make sure your DJ has professional grade equipment. Your guests will notice the difference between a high-quality PA system and a crackly old set of speakers with a stack of scratched CDs. Research the manufacturers that your DJ uses to find out if they are industry standard professional grade equipment.