After narrowing down your shortlist to one or two potential photographers/videographers; Set up a meeting with each of them in person or either through a phone call, video call or texting to know if you feel comfortable around them.
The importance of this cannot be overemphasized; this meet up will help foster a cordial relationship between you and your selected photographer.
You'll be spending a big part of your special day with this person, being at ease will not only guarantee you enjoy yourself more, but they'll also get better shots. Win-win!
These are some questions you should ask before choosing a photographer; they are little bit lengthy so you can email them for better correspondence and for the sake of record keeping.
What is your area of specialization?
Here is why you want to know this; for example, you want all your pictures to be taken as portraits, to avoid a mix of portraits and landscapes you will want to go with a photographer that specializes in portraits shoots. A lot of photographers when shooting, use a mix of several styles of photography and it is safest and best to go with a photographer that likes to shoot the style of pictures you want.
Are my pictures going to be edited? Will I see the original copies first?
Find and book with these questions in mind.