All previous posts are good advice. There are two reasons why I quarter turkeys and don't smoke them whole. The first reason is that the legs take longer, and the breasts are prone to drying out. So, I like the option of being able to take the breasts out an hour early. The second reason for cutting them up is that we smoke a few birds at a time, and then wrap all the pieces separately and freeze them. That way, we can take a package out of the freezer and have a week's worth of sandwich fixins' to take to work with us. It's really convenient to have them all smoked up and pre-packaged in reasonable portions. Once you have a sandwich made out of homemade smoked turkey, you will never want to touch meat from the deli again.
Al's point about being careful with salt content is really good. The brine is important, but don't overdo is. I actually do a more dilute brine than the one suggested in that Cook's Illustrated link I posted (I guess I should have provided this disclaimer when I first posted that link!) because that way, I have more flexibility to leave the bird in the brine a little longer without taking the risk of turning it into a salt pickle!
Finally, Talihofarms says apple juice in the brine - that's delicious. I like to brine with apple juice and smoke on apple wood. (You can't actually taste the apple in the smoke, but I still think it's a good combo.)
(Edited to add the following
You can experiment with brine flavoring. I have had good luck with a terriyaki brine that I adapted from a smoked salmon recipe, with soy sauce instead of salt, and brown sugar and red chilies. Also, once the bird is brined, but before it's smoked, you can put on a dry-rub with your favorite barbecue seasonings. There is no end to the experimentation you can do.
