There are tons of websites that give lists of good questions, but here are some that I've been asked that stick out:
- How many weddings have you done?
- Do you bring backup equipment?
- Do you have a backup photographer?
- Do you edit the images (retouch) before I see them?
- Do you let me see all the images that were taken (or most)?
- Are you full time?
The specific answers aren't as important as the way they respond. Are they confident? Is this something that they've thought about? Do you get the feeling they're hiding anything?
I would make sure the samples are what you'd want (portraits? Candid? What they display is probably their strong point. Don't expect something you don't see!) and make sure the personality fits well. You'll be spending lots of time the day of the wedding with the photographer, make sure it's a good fit!
That's what I recommend. Anyone else?
Shan