First impressions count. Though your work, or word of your work, often precedes you as a photographer.
There are many practical questions that you might ask your potential photographer:
Packages and what they contain
Qualifications or membership of professional bodies
The main thing to ask yourselves, once you've decided you like the photos, is really can you stand to spend several hours in the company of this relative stranger! (you'll have your share of strange relatives...but that's another post for another time)
A wedding photographer will (or should) have good people skills, be able to draw a smile from the dourest Scottish patriarch. He or she should also have the good sense to get out of the way when the couple need a break and some time together.
I believe that a good photographer has to be flexible, adapting to what the couple want and need from their photography, I also need to be giving them realistic expectations within the constraints of time and location.
For most couples I will meet this is their first time down the aisle, so they will not always know the questions to ask, they might have checklists or inspiration from a magazine, or will have no idea what they actually want. So when I go through my spiel, show my wares and a broader selection of past wedding photographs, I also try to go over the ins and outs of the taking of the pictures. Some formals are always handy for family or the wall, some reportage is nice to capture the moments amongst the wedding party and guests.
Opportunity, time, light and subjects permitting I adapt and flex to the demands of the couple and the day!
Having visited the Scottish wedding Show up at the SECC today as well, I saw similar skills in play from the photographers there. Most snappers had their wares on display, some arguably better than others, but the ones that seemed to draw more than passing interest, were the ones that took the time to sit down with the prospective customers and talk to them. Many of us use the same labs or suppliers, a certain level of technical skill is a given, but dish out all the flashy leaflets that we want, design the best beels and whistles packages, and we won't make the same impression as the person who listened to what you wanted and made a connection.
Now I just have to work on some newer sample albums and photo books to bring myself up to date!