A - Form a first impression through recommendations of others, viewing the web, and a phone interview. You may also wish to check with the Better Business Bureau before proceeding. Check availability.
B - Check out about 3 DJ's to find the one that best suits you. If you are dealing with a company, make sure you can meet the DJ who will be at your wedding. See if that person's style and music selection is what you are looking for.
If volume might be a concern to some of your guests, ask if that is adjustable on the evening. You can ask what is done to get people of all ages on the dance floor and having fun. Some DJ's are willing to do part of the MCing, so if you are interested, ask if it is possible.
As you are interviewing the DJ, get a sense of his or her personality. Are they confident, knowledgeable, and professional? Do you think this person could motivate your guests?
C - Check the references. Ask about things such as punctuality, politeness, and dress code as well as how well they "read" and motivated the guests. Ask what they liked, if there were any problems, and if they would recommend this DJ.
D - Sign the contract. Make sure it includes the location, the arrival and exit times, the final cost with hidden charges (such as travelling) and HST/GST. The frequency and length of breaks are important. If there is to be back-up equipment and a stand-by DJ, that should be included. Overtime and cancellation policies also be in writing, as should the fact that the DJ carries insurance.