It may be years from now when you realize the importance of having hired a good photographer. First, don't hire a relative, unless that relative is a professional. Just because Uncle Ira wants to do you a favor by shooting your pictures isn't a good reason to let him. Tell him you'd be happy, of course, if he'd like to bring his camera to take snapshots for himself. When selecting a photographer, ask friends, family and co-workers for referrals.
Word of mouth is the best way to select any vendor.
Still, it's always good to do your own research. Next, set up an appointment with three or four or more and make sure you actually meet and talk with the photographer who shoots weddings. Look at as many photos as he or she will show you. If you don't like the style, leave courteously. Many couples are choosing to limit the number of posed pictures and are requesting less-intrusive candids.