If I have to hire a wedding photographer for my own wedding, my criteria would be the following:
Recent Work: A photographer may be good in the past and may have lost track in the recent time owing to various reasons. Therefore, it is important to look at the recent work.
Complete set of pictures: Any photographer may be able to click few good pictures from each of their wedding shoots and showcase them on their portfolio. However, the real test here is whether he/she can provide complete coverage of the event and get most of their photos right in any situation. I would not want few pictures of my wedding to be of exceptional quality and rest being simply average or substandard. I would expect at least 70-80% of the photos to be of good quality. Therefore, you must ask your photographer to show you a sample coverage for one particular client and do a reality check.
Team: No honest wedding photographer would ever claim that he/she can cover the entire wedding on his/her own. Wedding photography is always a team work. Therefore, I would ensure that the photographer has a good team and they can coordinate well to provide complete coverage (traditional+candid) of the event.
Equipment: If a photographer does not have the right set of equipment and lenses, the chances are he/she will struggle real hard to click good pictures. Most of the weddings do not happen in the perfect photography condition. It is always more like a chaos situation. I would want my photographer to be prepared for the worst and be technically equipped to handle any kind of situation (bad lighting, equipment failure or damages, etc.)
Experience: The number of years a photographer has been doing wedding photography may have great impact on the quality of his work. Usually, I would not want a novice or amateur photographer to cover my wedding as wedding is a life-time event and I would not risk my wedding photographs with a novice/amateur photographer, no matter how promising his recent work may be.
Budget and Timings: This is one of the most important aspects of choosing a photographer. My photographer should be accommodating enough to fulfill my requirements within my budget and be flexible with the timings. I would not hire a popular or well known photographer, as they are the ones most likely to send escalated (overpriced) quotation for their services and finicky about the timings or slight delays in the event completion.
Reviews and Feedback: Wedding photography is not all about getting quality pictures but also about overall quality of services. The most important criteria for me to hire a wedding photographer would be to know the overall experiences of his/her earlier clients. This may help me find out how he dealt with his earlier clients, whether he was punctual at handing over all the deliverables, and most importantly, whether the client was happy with his/her work. Reading some genuine reviews may give you great insights about the photographer’s work and help you take an informed decision.
This is my honest answer to what I would look for in a wedding photographer, if I am getting married tomorrow. For a moment, I have tried to put myself in the shoes of a prudent client who cannot be easily duped by few fancy pictures or gimmicks.