It's all about the Zone System for me now. If you know how to take advantage of this, when concerning yourself with exposure, the background becomes your friend not an enemy.
That is from the aspect of getting the right exposure, it doesn't cover aesthetics. I always do a walk-around and envision the shots that can be taken from various angles. If I have the time or I come the day before to scout out the place, I do test shots. That way I know what potential challenges to expect such as white balance, extreme conditions and what not. I look for places that will give me the results I see in my head.
This info gets jotted down on a paper and used on the day of the event.
I try to do as little as possible in photoshop, but obviously, if needed, some things are done there... but very little and never very aggressively. I never do things like background changes, but my mentor, only when asked would do the corny stuff like the faces or rings in the champagne glass or the elaborate collages and similar tacky stuff.
Also, at weddings, you can do all the planning you want, but chances are good that they will drastically change. In the end, you do what you can and go with the flow for the rest.