Not drying it thoroughly before roasting
If you want crispy skin on your turkey — and who doesn’t want crispy skin? — pat it dry thoroughly with paper towels before roasting it. If you have the time, leave the bird in the refrigerator for a few pre-oven hours, unwrapped and on a platter large enough to hold it with no overhang (so that the juices don’t drip). The arid environment in the refrigerator will dry the skin more efficiently that simply blotting it.
Not trussing the bird
Once the turkey is well-seasoned, it should be trussed. Trussing a bird means tying it into a kind of bundle so that it cooks more evenly and the extremities (like the wing tips) don’t burn. There are many step-by-step instructions for the process online and in cookbooks, and a number of instructional videos on YouTube.
Not seasoning it all over
Some people like to rub butter or even duck fat on the exterior of their turkey before seasoning it. That’s fine, but it’s not essential. The seasoning part is. Once the bird is trussed, rub salt and pepper inside the cavity (don’t worry about the stuffing; see below) and then over every inch of the exterior. You may think you’re using too much seasoning, but you’re not. When you finish this task, though, wash your hands very thoroughly with soap and warm water.
Not using a roasting rack
The point of setting the turkey on a rack is that it allows the oven heat to circulate evenly all around the bird. If the bottom of the bird rests on the pan bottom, it’ll end up damp and pale. If you don’t have a roasting rack, ball up a few pieces of aluminum foil and scatter them around the bottom of your roasting pan and set the bird on top of them.
Putting the stuffing into the bird
Yes, generations of home cooks have roasted their turkeys with the cavities filled with stuffing and survived. But the stuffing, which usually involves breadcrumbs or some other porous substance, absorbs the raw turkey juices as the bird begins to cook, and those juices are often contaminated with bacteria. If you do stuff the turkey, the USDA recommends that both the meat itself and the stuffing are cooked to a temperature of at least 165 degrees F for safety. But the stuffing cooks more slowly than the turkey because it’s farther from the heat and by the time it gets to a safe level, the meat will be way overcooked and dried out. Bake the stuffing separately in a pan or casserole dish, and if you want to put something into the turkey cavity, make it a few bunches of savory herbs and/or a lemon or two.