Place the turkey in a roasting pan, preferably one with a rack, and tent it well with foil. I always pour 4 cups of water into the bottom of my pan and I never baste my turkey through the cooking process. I usually cook mine (average size 15-16 lbs) at 325 for about 4 hours. As a general rule, 15 minutes per lb of turkey usually gets the job done. The more frequently you open the oven door and check the turkey, the longer it will take. Oven temperatures vary though and after about 3 hours, I always start checking the temperature.
The real goal of cooking any turkey is to not dry out your bird. There isn’t a secret, there isn’t a magic trick, simple use a thermometer and remove your bird when the thigh meat reaches 170 degrees or the breast meat reaches 160 degrees. The temperature will continue to rise as the turkey rests on the counter. The goal temperatures are 175 for the thighs and 165 for the breasts. Following this rule has never failed to produce moist and flavorful breast meat. That is the most important part, right? ( I actually prefer mine without the gravy, but it looked naked in the original picture. So, here you see it fulled dressed in gravy. A turkey should never be so dry that it requires gravy in order to be eaten!)
Always test whether the meat is done by using the thermometer. Never cut through the meat to check the color. I can’t tell you how many meals I dried out by cutting into perfectly cooked meats and letting all of the juices flow out into the pan or onto the cutting board. If you do no have a thermometer, you can spear the breast with a sharp knife and make sure the juices run out clear and not pink. However, you should be extra careful not to actually cut open the breast too much as you are checking this way, or you will dry out a portion of it.