I plan for every possible scenario - and then a few 'impossible' ones for safe measure.
Do you have backup equipment?
I have several sets of backup equipment; even if I fall down a mountain, loose my luggage, and your good 'ol aunt Karen spills her whiskey sour all over my camera gear (wow, what a day) - I'll still be ready to go!
Are you insured?
Archiving / backup of our images?
I photograph weddings with no less than 2 cameras at a time. I have 2 separate memory cards within each camera (for a total of 4 actively used memory cards) that contain your photos, should one of them fail for any reason (it has never happened, but I like to be prepared). Once the day is over, I backup your images to 3 separate locations.
Once your final images are finished, I will deliver them to you electronically. I also backup those finalized files to 3 separate locations, just in case your computer crashes or you loose the files.
I once heard a story from a friend who hired an amateur photographer for their event; they didn't backup the images whatsoever, and the single memory card they used was somehow corrupted. The clients lost everything, and the photographer couldn't retrieve the files. Talk about terrifying; just one of the many reasons I backup everything!