I hate to restate the obvious, but...
Luggage and bags: Don't bring backpacks and stuff like that if you're visiting in the warmer months of summer. You`ll be constantly bumped by other tourists and you may end up wishing you had left them in the car (the bags, not the tourists). :-)
Clothing/Shoes/Weather Gear: I suggest NOT wearing flip-flops, despite the sand and sea around the Mont. There are a lot of cobblestones and steps that can't be avoided. You'd think I'd know this after all this time, but I bought a new pair of flip-flops and just wanted to show off, I suppose. :-)
Camping/Beach/Outdoor Gear: You could wear shoes that are easy to slip on and off, if you want to walk on the sandy beaches that surround the Mont.
- Historical Travel
Pack a Sweater & Umbrella
Luggage and bags: Only take small bags as I noticed that they have a back check at the entrence and it id not look like they could accomodate large bags.
Clothing/Shoes/Weather Gear: Most definitly I would suggest the following in your packing list... 1. A Sweater as it gets cold 2. a Rain jacket or umbrella as the weather turns quite quickly to rain. 3. Water proof shoes if you plan to wander the mashes ( Obviously with a guide)