Here is a pretty basic, yet informative, list to get you started giving consideration to some of the factors in hiring your photographer.
// STYLE //
Look at the photographer's portfolio + blog. See if you have an initial connection to their images. Do you like the lighting/colors/posing? Then, see the types of weddings and sessions they post... Is this more-or-less the *style* of wedding or portrait session you envision? One of the larger, determining factors of price is the studio-*typically, a larger studio with multiple photographers, or a studio that contracts local photographers is *traditionally* going to be a little cheaper and offer a less stylized/connected approach to the wedding; whereas, a *boutique* studio, or a 1-person operation, can sometimes be a little more expensive, but you would be hiring their body of work, personality, photography style,etc. But that's certainly not always going to be the case, as there are always exceptions on both sides...!
// SERVICE //
I would definitely check to confirm the photographer has backup equipment and a 2nd shooter for the day. You are also going to want a photographer that is willing to sit down with you, via Skype or in-person, and have an initial consultation going through their packages, products, approach to photography and finally, an introduction to how to schedule the wedding day. No matter how low-key or high dollar the wedding, you always want to have a pretty solid timeline for what is happening so your photographer knows where to be and when to be there.
// PACKAGES //
Comparing photographers and their pricing is not always as simple as comparing apples to apples. The main differences you will notice in packaging structures are the number of hours of coverage, additional sessions (engagements/bridals), products such as prints + albums, and most importantly--the delivery of your images. Do you get the digital negatives that you can print yourself, or do you have to print through the photographer? Are the images delivered on an online proofing gallery, on a USB or DVD, or can you purchase either of these at an additional cost? Just some things to think about!