how long to cook a turkey...............really?
Use an instant read thermometer not a clock. I take mine out when it is 10 degrees less than it should be at the end because of course it keeps cooking while it's resting. I also rest my "tented" turkey for 30 minutes before slicing it.
It depends on your oven, the size of the turkey, whether it will be stuffed or unstuffed. The chart provided by TiggyBee is a good start. Begin checking for doneness about 45 minutes before the time suggested. If you have a thermometer, the meat at the thickest part of the thigh should read 155 degrees--it will go up to 165 degrees within the half hour that the turkey needs to rest before carving, but it will stay hot for another hour afterward if it's not carved right then.
If you don't have a thermometer, pierce the thigh with a skewer--if the juice runs a little pink, remove the turkey from the oven, but if it runs red, leave it in for 15 more minutes and check again. Don't rely on the "shake hands with your turkey" method to test for doneness--if you move the leg up and down and it falls easily away from the body, the white meat will be overdone. And dry.