Make sure you look at their work. Have some sort of theme or wardrobe in mind so you can save money on the planning (if the photographer charges for consultation). Ultimately you are the client so don't be afraid to tell the photographer exactly what you want the finished product to be like in the end. Interview them and make sure that they can do what they say. Do a background check on them via Google or something so you can have peace of mind while it a photoshoot.