The right wedding photographer will capture and reserve your wedding day for a lifetime. If he / she is doing their job right, they should be documenting everything- as it's happening. Sure, we all have seen the obvious posed pictures that mom loves but the end result should be a time line using only images to tell the story.
One thing you may want to consider when hiring your photographer is simply, how many photographers will be at your wedding? Make sure you ask who will actually be shooting the wedding, as well. You may be dealing with a salesperson when you should be dealing with the photographer. If their is a "second shooter" find out if they are an assistant or a real photographer? An assistant may look like a photographer at first glance but in reality they are usually trainees or $ 10 an hour helpers.
Why are two better than one?
Having two photographers will give you many advantages. One advantage is you will have twice as many images to choose from and multiple angles of the same shot. While you and your bridesmaids are smiling at the main photographer, the second shooter will be getting the same image from a candid position. I have noticed that a lot of my clients will choose the candid image over the "looking at the camera" angle. Having a second shooter will also give you much wider coverage of your wedding. While the girls may be taking forever to get ready at the hotel, the second shooter can be with the guys at the cemetery site (or in many cases, at the bar!) be priceless. Having 2 photographers can also save a lot of time, if you are having time issues.
There are many other factors when making up your mind about a photographer. Seeing (and liking) their work is important but your personalities clicking is even more important. You'll want your photographer to blend into your wedding party. This will help capture the emotions going on in the room, and let you feel more comfortable showing those emotions. Sometimes your photographers appearance, age, or even sense of humor can make or break the deal. (same goes for DJ's, too!)