First and most important thing...make sure you get it NOW, and make sure you start defrosting it with enough time to finish before cooking. Nothing worse than waking up on Thanksgiving morning and realizing you've got a frozen turkey. Oh, and just to be easy, get one with the pop-up thermometer.
Second, get lots of chicken or turkey broth, as it always comes in handy.
Take it out of the wrapper. Reach in the bird's butt and pull out the sack containing the innards and either toss 'em, or set them aside. Put the turkey under running water and just rinse it off, inside and out, then pat it dry with some paper towels. Stick it in a disposable aluminum foil pan (unless you have or want to buy a real one), and if you want to stuff it, now's the time.
For stuffing, just get some pre-packaged stuffing breadcrumbs...you'll find these in any and every grocery store around the holidays. I prefer the stuff with herbs and crumbs instead of cubes. Follow the directions on the package, withholding a little of the water/broth...add broth to suit your tastes for how dry you like it, but keep in mind that any you stuff into the bird will pick up moisture in there, so put it in a little dryer than you like it. To add some flavor, you can whip out the sack 'o' innards, and toss everything but the liver and kidneys into a small pot of boiling water until they're thoroughly cooked, then pull out the neck and set it aside, and put the rest in the blender until it's well chopped and use that in place of water/broth. Don't smell this mixture, and don't let any delicate-types see you doing this or they might gag and cry...the end result is goodness though.
Stuff the bird, but don't pack it in too tightly. Put a couple of cups of water in the bottom of the pan to help with gravy production and to keep the drippings from burning and smoking. Melt some butter, and add in some fresh herbs, and brush it on the bird (optional, but yummy). If you're using a cheapie foil pan without a lid, put some foil over the bird...stick some toothpicks in the bird to keep the foil off the skin, so it doesn't stick to the foil. Cook it according to the directions on the package. Baste it every hour or so (or don't, whatever). Pull the cover off for the last 30 minutes of cooking to get the skin nice and browned. Let the bird sit for ten or twenty minutes before carving it up.
Make gravy with the drippings...use a new pan, or just use the pan you cooked the bird in, and set it across a couple of burners...cheapie foil pans don't work well for this though. You might wanna use a baster to suck up any excess grease/oil/butter off the top of the drippings...or you might not. Get it hot enough to boil, and KEEP STIRRING. Mix some corn starch or flour with some water to make a thich roe, and mix it in with the drippings a little at a time. Keep stirring until it gets to gravy thickness. Have bottled gravy as a backup - depending on what kind, it's actually not that bad.
Don't forget the corn. Corn is important, and corn is goodness. You should have lots of it.
Also, buy real cranberries, and make real cranberry sauce. They'll have directions on the package...it's simple if you pay attention, and well worth it.
Finally, eat until you feel like you're about to die. Then, continue eating until you pass out...try to stay leaning forward when you're near the point of going under, 'cause it'd be embarassing to choke to death on the food that's in your mouth when you pass out.
After Thanksgiving...Turkey Sammiches!
Just remember - it's not rocket science, it's just cooking a friggin' turkey. Even if you mess up, it'll still be good.
Underdone is solved by more cooking.
Overdone is solved by more gravy.
