I understand that for most people, choosing a DJ is often difficult and confusing, yet the most important decision you will make for your Wedding Reception. Since everyone claims to be "the best", how can you really find out who is good, and who is an amateur? For a once in a lifetime event like a Wedding Reception, you best start with a professional. Don't take chances with "a friend of a friend". Although people mean well, lack of experience or skill will not prepare them to handle unexpected details.
First I recommend you start with a wedding specialist. A DJ from a club or school dance may be great, but they're not necessarily right for you wedding.
Second, meet with the DJ. This is not a decision that can be made over the phone. You must be sure you are comfortable with the DJ's style and see if it is a good match for you. After all, they will be representing you at your Wedding Reception.
Then, check the history and background of the DJ Company. Do they have references? And don't just take their word for it, call several of their references and find out WHY the client loved their DJ.
Don't make the mistake of choosing a DJ by price alone. If the DJ is not a good fit, but the right price, it won't matter a bit if he ruins your special day that you spent big money and many months planning.