Before we discuss professional and technical qualifications, I want to stress the importance of style and personality in choosing a photographer: Photography is a very personal thing. No matter who's event I'm photographing, the images I present in the end are still a reflection of how I see weddings, and how I saw your wedding in particular. To ask or expect a photographer to change her style just for your wedding is like asking a rock musician to switch to classical "for just this one concert".
Look at the samples the
photographer shows: Are there an abundance of posed portraits or heaps of candids
and photo journalistic shots? Are the albums designed and laid out in a way
that looks good to you? Is there black and white coverage mixed in or is it
all color? Is this what you want your album to look like? If not, this is not
the photographer for you.
Do the pictures and albums speak to you? If they don't,
this is not the photographer for you. Make sure that the photographer's vision
and style mesh with yours or you will be disappointed.
The Photographer's personality is also of the utmost importance. Make sure you truly like and get along with the person who is shooting your wedding. Remember that you will probably spend more time with your photographer on your wedding day than with any of your other service providers. Your photographer will have to give you and your families directions at some point and needs for you to be willing to listen and follow his directions, especially if you are having a more traditional style of Wedding Photography with posed shots that require the organization of many people. They may or may not have to touch you to adjust a veil or a bow tie, move a strand of hair, etc.
If you don't like this person, or are uncomfortable around them, your pictures will reflect it. Even if the samples you look at are stunning, you will resent the requests and instructions of your photographer and it will color your perception of your wedding day.