It depends on where you're camping, and the conditions. I do almost all my camping in the desert, high desert, or the higher elevations of the Great Basin, etc. -- so mostly dry weather.
I bring a dome tent suitable for two, but almost never use it. I prefer sleeping under the stars.
I use one of those ubiquitous blue tarps, about 10' x 10', as the base. When camping alone, I use it folded in half. On top of this I place a foam sleeping bag pad, and then my sleeping bag.
If I do get rain, most of the time I'll just move some gear out of the back seat, and sleep in the folded down the driver's seat. I usually don't set up camp until late evening, at least, and am on the move again in the morning, so setting up the tent isn't worth the trouble. (And in summer weather, a tent is too hot anyway.)
Food: Obviously this is a very personal choice. In my case, I don't hassle with cooking anything when I'm camping. It's a huge waste of time and energy. I bring some quality roast beef, cheddar cheese, lettuce, bread, mustard, and make sandwiches. I also bring plenty of chips, some black olives, and a few of the small, pop-top cans of Bush baked beans (good straight from the can!)
For breakfast or a quick snack, I bring along some bear claws and/or danish, cut in half and stored in Rubbermaid containers.
Drinks: Orange juice for breakfast; lots of diet sodas and Lipton Brisk iced tea; and V8 juice.
Food and drinks are kept in two large coolers. One cooler is mostly for cold drinks, the other mostly for cold food. Extra drinks, etc are stored in the vehicle and added to the cooler as needed. And of course, a can opener and a few utensils, matches, lighters, etc for "just in case".
I bring a change of clothes for each day of the trip, plus a jacket or coat, and any other item that may be needed.
Besides basic tools, I also bring folding camp saw. It's great for cutting away branches that have overgrown the trail.
I have a couple different flashlights I bring, with high intensity LEDs. Also two different kinds of UV flashlights -- fun for finding fluorescent minerals, and useful for spotting scorpions. I also bring a couple battery powered lanterns that are handy around the camp or in the vehicle.
