When interviewing with your DJ, should the first question be, what is the price?
Chances are if that is your only concern, you may end up telling your story on a blog or wedding site about the nightmare $100 DJ.
Like any other product, where it be a car or a pair of shoes, you should give it a good look and if possible a test drive.
Although, you can't actually test drive a DJ, you may be able to see footage of previous events he/she has performed at; yes believe it or not it is a performance; not everyone can stand in from of hundreds of people and be comfortable at what they do. Another option is to see the DJ perfroming live (recommended only at benefits, corporate events and the like); chances are you may NOT be able to sit in a live wedding reception for you wouldn't like for YOUR DJ to bring a total stranger to your own wedding reception.
What personality is that your DJ should be. Fun, energeric, no real preference? Does the DJ sound like he is going to put you and your guest to sleep or have them involved?
Does the DJ sound like he knows what he is talking about; experience counts for a lot at a wedding reception. Season vetarens, know how to keep the event flowing and will get involved with your planning, cordinating with your other vendors throught the entire event. It is not a one man show.
Music is what most people relate to a DJ, how broad of music knowledge may also be a concern for you. Although most of your piers may like top 40 music, wouldn't it be nice to have your Mom and Dad, Aunt and Uncle and other siblings have a turn on the dance floor? An experience professional will know what would be appropiate.
The above is just a few ingredients of what should be asked in addition to the price.
Any suggestions, please feel free to share with us.