When hiring a wedding DJ, make sure that you have an interview process with them. This means talking to them about who they are and why they are DJing in the first place. You want to get a feel for the type of person that you are paying to perform at your wedding.
A great way to find a wedding DJ that is perfect for your needs is to actually talk to friends and family. You can find out who they used for their own wedding and you will be able to find out how wasn't as good as they thought that they would be.