You're off to a good start. You've got shelter, table, chairs - add a cooler and a grill and you're set. Then grab your buddies and head to the game extra early to setup. They'll need a ticket or a tailgate pass ($10) to stay there during the game. Tell them to get a ticket - they'll want to go in.
My advice - keep it simple.
1. Think of foods that require minimal prep work so you don't spend all your time cooking. Do any pre-prep the night before (slicing onions, making hamburger patties, etc.
2. Use disposable bags/containers so you can toss them. You don't want a pile of dishes when you get home. Bring trash bags to make clean up afterwards easier.
3. Don't try to be the biggest & the best. There's plenty out there, the idea is to have fun. Our group doesn't have meetings or dues, or cover charges - it's like a big pot luck of extreme proportion - but it works. Find out what works for you and do that.
4. Make a tailgate box so you don't have to hunt down your stuff the night before the game. Don't share with your current kitchen goods - you'll forget something different every week if you do.
5. Bring Entertainment. A football, bean bags, washers, etc. Bring a radio and plug an ipod with a pre-made playlist so you don't have to mess with it. If there are kids, bring something for them.
6. Call your friends from the parking lot & rub it in that they're not there.
Don't sweat the small stuff & Don't forget to have fun!