Tailgate camping packing list is the second longest (second only to RV camping).
I suggest doing a few trips to the Primitive Campsites in the parks near you first. It's a great learning experience to get you prepared. Check (link)
local parks and try out a few. Most federal and state parks will have campground maps so you can pick out something isolated before you leave the comfort of your fuzzy slippers. You'll find a site or two that are fun and just far enough away from everyone else to test out your setup.
For first-time tailgate camping, remember...you can't have too much.
Just take everything (link)
INCLUDING THE KITCHEN SINK! Load up is my suggestion. I pack the Jeep to the roof and beyond when I go on try-out trips. When I'm camping, I keep things set aside that I use and bundle up stuff that I don't use. Take a notepad and make notes about things that you take.
Think about what you like doing when you're away from the Playstation and make your over-packing list accordingly.
Do you like cooking? I do. I take a tri-fuel two-burner stove and a (link)
campfire grill. On top of that, my cast iron dutch oven, cast iron pans, BBQ and regular kitchen cooking utensils, cleaning gear, etc. I ALWAYS take at least one camping table. Even when there's a picnic table, having your own folding camp table is PRICELESS! Trust me, you won't want any of your food to get close the those picnic tables. Nasty. You might also think about a thick table-cloth (a spare tarp works fine for this too). I also take full-size hard plastic plates and full-size metal eating utensils. I have camping utensil sets, but they really suck compared to the real thing.
Like playing card games? Take at least a couple decks of cards. You'll lose a card or two, so having spares is nice. Oh, and I suggest playing for Cheetos or you'll lose a few of those nice poker chips in the dirt.
Like music? We take guitars, harp, and I even take a make-shift drumset along when we're tailgate camping. Like music, but don't play? Bring a radio or iPod (and speakers).
I take the biggest tent that will fit in the area I'm going to. The park ranger will be able to tell you specific site sizes when you make a reservation. I have 4 tents, so it's easy for me to adjust. If you only have one tent, give it a shot, make notes, and purchase your next tent accordingly.
Tailgate camping = airmattress or cot. I used to just take a tri-fold lawn chair and use it as a cot. Works fine as a cot long as you put something beneath the head part so it won't bend and be resting on the ground when you wake up. Nowadays, it's an air-mattress. Although, I'm now shopping double-bed sized foldaway cots.
I usually do not take wood along with me. Some campsites are beginning to suggest NOT bringing your own firewood as it (according to their signs) "can spread alien species into the local environment." You can get it at the campsite, or you can usually find a nearby farmer who will sell you much better firewood for less than the campsite sells it for.
HEADLAMP. Get one. Get two. PRICELESS!!! Set up a tent once without a headlamp and once with a headlamp. Then you'll go headlamp shopping again to find a better headlamp than you already have. You'll end up like me and have 4 headlamps. You'll also find that the headlamp is one of the first things you pack.
I also always have my lantern and a couple other flashlights too. I have a waterproof Coleman flashlight that converts into lantern that has proven to be very handy. It's also one of the cheapest flashlights I've ever purchased. Expensive does not mean good. Buy something and try it out on a trip. I bought a Gerber flashlight and took it camping. I ended up throwing it away before the first night was over. It wasn't even worth giving to someone.
First aid kit. If you don't already have one, get a pre-built one. This is something that you will never regret having.
And keep in mind; Like a good Jeep, a good camp-site is never "done." It's a dynamic process.