Start a checklist today. Make a list of everything you need to accomplish over the next seven days to be ready for guests. Don't wait until the last minute to begin marking things off the list! Plenty of things can be done a few days early, such as ironing tablecloths and polishing silver. (Or pulling out the paper plates from the summer party bin... lol)
Plan your meal out in paper (or document!) - this helps you remember any forgotten ingredient you might still need to purchase. No one forgets the turkey, but it's easy to forget the smaller things.
Ask ahead of time if anyone has any special diet requests. As we get older, some of us are on low sodium diets, become vegetarian, or have to watch the sugar. In order to not leave any one out - or to offend someone's new husband or wife - don't be afraid to ask if someone needs a special side dish. Perhaps you can even hint for help from that person - ask for a recipe, and they might even offer to bring the dish instead! (And that, my folks, means one less thing to worry about!)
Many dishes can be made ahead and re-heated, such as green bean casserole and cheesy mashed potatoes. Don't be afraid to keep side dishes warm by using your slow cooker! Chop any veggies the day before - they will be fine in the fridge. Pies can be created the day before and then baked at the last minute.
Most of all, BREATHE! What's the worst that can happen, the turkey blow up in your oven? Fear not, many grocery stores are still open on Thanksgiving - and you can always order pizza. Sit back and enjoy the time spent with your loved ones!