Check referrals. Ask your wedding vendors who they’ve seen and recommend. Photographers, videographers, and caterers are the best resource. Also ask family and friends.
Request a face-to-face meeting with your entertainment choice. This will give you a feel for the person and will determine if you have a personality match. After all, they will be representing you.
Request to see uncut video footage of the DJ’s performance. You’ve seen your photographer’s work, your videographer’s video demos, tasted your caterer’s food, and visited your venue, etc. Ask to see video of an actual introduction of the wedding party, the first dance, the cake cutting announcement, plus video of how the DJ interacts and motivates the crowd, etc. Any DJ can show dancing guests but you deserve to see more of what the DJ will do to create the special moments at weddings.
And finally, ask about continuing education and/or workshops that they’ve attended in the last 5 years. How are they improving their skills, education, talent, and more? There are several workshops that are available for skill and performance improvement. Your event deserves the best.