There are many direct and indirect ways to hire a DJ. It is often said that using an agency is best. This is not the case. An agency will have various DJ's on their books and will say they guarantee a replacement if your DJ is ill before your wedding day. This is true but is also true for any reputable DJ. A good DJ always has back up processes in place just in case. An agency will charge you a large commission (about 25%) for this but will pass the responsibility onto the DJ they have hired. It is most often part of the DJ contract with an agency that the DJ is responsible to provide a replacement if they cannot perform. Hire a DJ direct but have the contract reflect that they have provisions in place.