A great demo mix tells you a DJ has taste. It doesn't tell you whether they'll show up on time, handle a microphone, or notice that the dance floor emptied ten minutes ago. These questions fill in the rest.
Will you be the one at my event?
Some companies book under one name and send whoever is free that night. Ask who will actually be behind the decks, and whether you can talk to them before the day.
How do you plan the music with us?
Listen for a real process: a planning call, a must-play and do-not-play list, and a timeline for the key moments. "Just send me some songs" isn't a plan.
What happens if equipment fails?
The right answer involves backup gear in the vehicle, not a promise that it never happens.
What do you need from the venue?
Power, space, load-in time, and noise limits all matter. A DJ who asks about them early has dealt with them before.
Do you carry insurance?
Many venues require a certificate of insurance. Ask now, so it isn't a surprise in the week of the event.