Love Their Images....
I know it sounds obvious but you have to love their work. It helps if you feel an emotional connection to it. Don't choose your photographer purely based on other peoples' opinions . You've got to feel something when you look at their work! Make sure it reflects you as a couple. If you're laid back and outdoorsy, you probably don't want formal photographs.
I would also recommend checking that they have photographed real weddings and not just styled shoots. Often styled shoots don't involve other guests in any of the images. They are basically organised by vendors or photographers offering training. They are set up and don't reflect what the photographer can really do.
Ask to see some full galleries of their work. That will give you a really good idea of their style.
Hire a True Professional
The chances are, you've spent a lot of time and money organising your wedding. You've put a lot of thought in to every little detail and you want it to be just right. Don't waste all that effort by employing the cheapest photographer you can find, Or worse still, trusting your aunty Jean or uncle Bob (who just love taking photographs!) to document one of the most important days of your life. It's a lot tricker than you think.
Quite often the wedding photographer plays a massive role in your day. They help to organise guests and plan which photographs will be best taken when without disrupting the natal flow of your wedding or getting in the way. They have usually photographed lots of weddings before and are a good resource for help and advice along the way.
Most photographers wil include testimonials from previous clients on their websites. It's good to have a read through them and see if they resonate with you. Are the things that other couples are commenting on important to you? What do you want from your photographer and are the testimonials reflecting any of the things on your tick list?
Look out for several sources of reviews too. There may be reviews on their website but google is also a good place to look.
Like Your Photographer as A Person
You'll probably be spending a large portion of your wedding day being shadowed by your photographer. Make sure you like them on a personal level. Either meet in person or on a zoom call before you book them. You should feel comfortable with them and feel like you can relax and have fun. Like having a good friend by your side. It's also an added bonus if they make you laugh!!!
Value for Money
It's good to know what you are getting for the money you pay. How much experience does your photographer have, how many images do they provide you with and are there any hidden extra's to pay? These are all questions to consider before booking.. Some photographers offer complimentary pre-wedding shoots or prints that may be worth taking into consideration. You may also have access to two photographers which is great if both parties want photographing as they prepare for the ceremony. This is also a great way to get the more traditional shots of the day, but lots of little extra's that you might miss too!
Remember that your photographer should also have insurance in case anything goes wrong on the day (that's very unlikely but checking they are insured should give extra piece of mind).