Ceremonies fall into two major categories: indoor & outdoor. Each of these come with their own sets of limitations that will affect the look of how my couples' images will turn out, and present their own wonderful creative challenges.
Indoor ceremonies are often limited by low light levels and mobility--there are only so many pathways through the space, and the light tends to be less bright and airy than what you find outside. But in most cases an indoor ceremony offers consistent light, which makes tricky camera settings more predictable.
So for the indoor ceremony, my priority is moving around as quietly and as quickly as possible to get the shots I need. Usually I'm competing for the same aisle space the participants are, or crouching next to a pew, chair, or bench. While my goal is to be unobtrusive and fast, I also focus on effectiveness -- even with a silent shutter, the subtle noise caused by my motions can be a distraction. I shoot what I need to get the shot, but make sure I'm not making a racket.
While offering a greater volume of light (the SUN) and mobility (flexible pathways), outdoor ceremonies are limited by weather conditions. Depending on the time of day, the light could be beating down heavily on a ceremony space, or perhaps it decided to rain and make the ground super squishy.
So my goal is to ultimately get the shots you want without being obnoxious (stepping in front of the parents), but being daring enough to get close (unless there are ceremonial or religious restrictions to be observed).
So I've been allowed (and expected to be) up super close in the middle of all the prayers and rituals, using a wide-angle lens to capture the environment & action.