1) Meet them. Are they trying to understand and fulfill your wishes or are you another package to sell?
Would you feel comfortable inviting them to your wedding?
2)Ask to see 30-40 photos or an album from a recent wedding. Are all the photos good? Is the album well designed?
3)Are they willing to give you the hours of coverage that you want? Many of the best photos are during preparation and after the guests start to leave.
Clock watching photographers don't get those images and they can interrupt your reception as they leave.
4)Beware the newbies. Weddings are fast moving and require great skill both as a photographer, and as a gentle herder of cats.
Newbies often fail to produce the happy day and great photos that you deserve.
5)Choose a photographer that wants to photograph you wedding.
Beware photographers who want to direct a photo session where they control, interrupt, delay you and your wedding. This destroys the flow and fun of a wedding for lots of posed photos of guests biting their lips.