PLEASE NOTE: The following tips are from random couples, with different experiences.
These days, when the "PROFESSIONAL" term is outdated, you should look for an EXPERIENCED and REPUTABLE photographer, who has ONLY REAL WEDDINGS on their website, rather than "styled/staged" photo sessions with models. Those samples DO NOT REFLECT the photographer's work in REAL TIME and with REAL COUPLES.
By asking the RIGHT QUESTIONS, you will definitely know who is the RIGHT PHOTOGRAPHER for you. Don't be shy. You are the PAYING CLIENT and demanding everything IN WRITING is your basic right. DO NOT TAKE VERBAL PROMISES.
So... Where to start...?
*** WEBSITE ***
Your first impression with someone, starts with their website. NOT Instagram. NOT Facebook Page. (Ask yourself do you really want to hire someone who can't afford a professional website for their business...)
*** ASK TO SEE 2-3 FULL (DAY) COLLECTIONS OF REAL WEDDINGS ***
The best way to check how the photographer REALLY works, is simply to ask them to show you photos from a full wedding. (naturally, websites present the "best" images of someone's work, but not always from REAL weddings)
*** BUSINESS & LIABILITY INSURANCE ***
Any experienced and established wedding photographer will have those, for obvious reasons. Some wedding venues, all national parks and even some indoor facilities you're planning your photos done at, will require a proof of a commercial (liability) insurance for $2M-$5M...
*** GEAR & BACKUP GEAR***
There's nothing wrong with asking the photographer about their cameras & lenses. (FULL FRAME camera and PRIME LENS usually means that the photographer has invested in the best gear and you are going to get way higher quality images) Ask about their backup gear!! ("...what happens if your camera falls, or stop working for any reason...?")
*** BACKUP PHOTOGRAPHER ***
VERY legit and important question! ("what happens if you can't make it to our wedding, for whatever the reason is...?")
*** DIGITAL IMAGES ***
This topic is a pretty grey area and most of the photographers will NOT disclose in full, but, you DESERVE TO KNOW - WHO will be working on your images AFTER your Big Day. OUTSOURCING the photographer's workflow (culling and editing) is pretty common these days, but YOU HAVE THE RIGHT TO KNOW ABOUT IT. (WHATEVER IS AGREED - GET IT IN WRITING!!)
*** ENGAGEMENT SESSION ***
This is the best way to check how your photographer works with "real" couple, who has no camera/modelling experience. Giving directions for posing, finding your flattering angles, making you comfortable in front of the camera, being able to show you the images as you shoot, from the camera's back screen (as is, no edits). (Experienced photographers usually offer this as a complimentary service)
CONTACT ME with any additional questions you may have.