One common mistake when checking to see if a turkey is cooked, is looking at the color of its skin. This is a misconception- that just because the skin is browned it is cooked.
Of course, high temperatures cook the outside first, but it in no way means the inside of the bird is ready.
The best thing to do to see if your turkey is cooked is to buy a meat thermometer.
Insert it in the thickest part of the breast. To be extra careful, you can also insert it into the thickest part of the thigh for a second reading.
If it reads 165 degrees, it is ready to take out.
This easy-to-read chart gives approximate cooking times in keeping with the size of your bird.