How important is a wedding photographer? Major important!   Hello, you don't get a chance to redo your pictures if they are messed up.

Before you book a photographer, you need to interview them to make sure you are on the same page.  You need to look at their work and decide if their style is YOUR style.  Your interview will let the photographer know what you expect and if they can deliver what you want in your budget. 

Ask questions:  
Will you bring two cameras in case one malfunctions?
Do I need to have a family member available to point out family members?
Do I have to make a list of shots that I want taken at the wedding and reception?
Will you take candids in addition to formal shots?
Is a video included in my package?
Will my photos be online so that out of town family can order pictures? 
Will you go to the wedding and reception sites in advance so you know the layout and what
lighting you'll need?

Decide what is the most important to both of you.   Do you need a formal portrait in advance? 
Do you want photos taken before the wedding so that you can enjoy the reception?
Do you want outdoor pictures?
If the pictures are taken outdoors, do I need to provide a sheet or ground covering so my dress
doesn't get soiled?

Ask the photographer if they will sign off on the copyright of the photos so if you want to reprint them
yourself, you are able.  The photo developers police the copyright vigorously.