How do you keep turkey from getting too dry?
I suggest using a brine. Lots of brining details can be found in the answers to this question:


  What are the basics of brining meat?


Alton Brown has a really great recipe for brined roasted turkey. You can watch the Good Eats excerpt on YouTube in which he covers brining turkey.

I also suggest reading The Basics of Brining (PDF) from Cook's Illustrated.