Don't use one. Unless there's some disqualifying factor (weather, temperature, insects, snakes), sleeping out in the open on a sleeping bag and mat is the most comfortable way to go.
Either way, make sure you choose your site carefully. Obviously, you want a flat area free from rocks. But also check that you're not setting-up in a place where water will run through or collect during a storm (especially avoid dry creek/river beds). In hot weather you want a shade and a good breeze. In the winter you want a location that is protected from the wind but not at the bottom of a gully or canyon where cold air will collect. Also pay attention to where the sun will rise and set, and which direction the prevailing wind blows, and the presence of any game trails or heavy signs of predators.
Then prepare your site by getting on your hands and knees to get rid of all sticks, rocks and stones. At the same time you'll discover if there's any animal or insect nests that might cause you reason to relocate. Decide how you want to orient your tent relative to the sun and wind. Then find dead, dry leaves, pine needles, grass, ferns, etc., and make a pile about a foot deep and the size of your tent. Spread your ground sheet over the leaves and then setup your tent on top. Make sure your ground sheet doesn't stick out further than the floor of your tent.
If you're using a camp cot instead of (or in addition to) a sleeping pad, use furniture coasters (plastic circles or squares used under furniture legs to protect the floor) to keep the cot's legs from sinking into the soil, possibly puncturing your tent floor. I've seen people spread out old comforters under their tent for padding/insulation (instead of leaves), but I can think of better things to carry for that space and weight, even in a car. I use sleeping pads: either a Thermarest Neoair when backpacking or an REI Camp Bed 3.5 when car camping: both are comfortable and provide some insulation from the cold ground. On top of that goes my Campmor 20*F rectangular down sleeping bag, which I'll sleep on top of if it's warm enough, or crawl inside and zip up. I also bring a silk sleeping bag liner that I can use alone in warm weather or with the bag in very cold weather. For a pillow I just stick the dry bag with my spare clothes inside a pillow case.
My opinion is that tents are for sleeping and changing clothes. If I'm car camping I bring a small door mat for outside the tent entrance and an LED/battery lantern for inside. But all activities other than sleeping or changing clothes happen elsewhere. So I wouldn't setup a table or chairs inside my tent -- too much temptation for bringing food or drink inside. When backpacking I'll string my poncho if needed to make a dining/sitting area protected from the rain. If car camping I'll have a good size tarp or easy-up canopy, possibly even a screen room for my dining and sitting area.