When you buy it, look for the company's brochure, which marks items acceptable on the Feingold Foodlist with a green star next to the product's name. That is a good way to have spoiled turkey, because the outside is warm while the center is still frozen. The directions usually say to defrost for several days in a refrigerator. If this is a problem, or if it is still frozen when you are almost ready to start cooking, put it in the bathtub or sink if large enough, and run COLD tap water over it. If you stuff your turkey, time it so that it is cooked about the time you are going to eat it.
Many turkeys have a timer button that pops up to show when it is done.
If not, check to see if the drum sticks are able to be moved easily, and the juice should run clear if you poke the breast with a fork. If it is cooked well before dinner is served, do NOT leave on the counter to cool for hours. Rather, get that stuffing OUT of the center of the bird so it can cool and not spoil. Some people never cook the stuffing in the bird, but only in a casserole on the side, which is probably very wise. Some come with their own directions.