Most of the time my preference during the ceremony is to shoot from the front, if I can do so without being a distraction. I may move around a little but again, I will always try to make sure that your ceremony isn't interrupted.
Some officiants have very strict rules about photography and I have, in the past, been told that I cannot photograph at all during the ceremony. It's best to ask ahead of time if there's a policy that we should be aware of to avoid disappointment. In some cases it's not possible to know ahead of time who your registrar/celebrant/vicar is going to be before the day, and each one may have their own particular rules. I will always endeavour to capture the ceremony as best I can but there's not much I can do if I'm given strict rules to follow.
These days every guest has a camera in their pocket. For the most part, guests taking photos isn't an issue but occasionally I have experienced obstructive behaviour such as guests standing in the aisle, shooting over my shoulder... even a selfie stick blocking key moments.
It's by no means compulsory but lots of my couples recently have chosen to opt for an unplugged wedding ceremony, asking for guests to be in the moment during that part of the day and save taking photos for later. It means I'm able to shoot without the dreaded selfie-stick situation. Here's some text that one of my couples chose to include in their order of service!
Our ceremony will be short and sweet, and we have a photographer who will be capturing it. We love you all very much and we cannot wait for the moment we turn around, as husband and wife, to see all your smiling faces for the first time! So please, no photos during the ceremony!
It works really well and means that I'm more likely to be able to get better reaction shots of your guests, present and in the moment.