A DJ may charge a flat mileage charge if the reception is outside of a particular area. If you are hiring a DJ from one area and expecting them to work the reception in another, be sure to ask about a travel of mileage charge. It may be more cost effective to find a DJ closer to where you are holding the reception if the charge is high.
Look for a DJ that has a good selection of music for all ages. Typically a wedding will include older and younger guests so having a good variety can really help in making the evening fun and exciting for all the guests, not just one particular group.