I actually happen to be smoking a turkey tomorrow for my daughter's and mom's birthday!
First piece of advice......BRINE!
If you have the time, brine for 24 hours in refregerator. Google "turkey brine" and you'll get the encyclopedia. A very basic brine is:
1 gallon water
1 cup salt
1/2 sugar
The most important thing is the salt/water ratio.
Anyway....brine for 18-24 hours. Then pull the turkey out, rinse with cold water and pat dry with paper towels. Place on rack back in fridge for a few hours to overnight to let the skin tighten back up.
Pull out of the fridge a couple of hours before the cook. Place bags of ice on top of the breast like this:
That will allow the breasts to start cooking slower than the dark meat, which will prevent the breasts from drying out.
THEN....
Fire smoker.
Bring temp up to between 325-350.
Smoke with fruitwood until 165 in breast and 180 in the thigh.
I like using a turkey cannon for mine when I can.
http://www.campchef.com/infusion-roaster-turkey-cannon.html
If not using a turkey cannon, I usually always stuff an onion (halved) a lemon (halved( and an orange (halved) in the cavity, truss it up and put it on a roast rack so it's easy to move on and off the cooker without tearing the skin. You can also just put it directly on the smoker cook rack.
Mmmmmmmmmmmmmmmm......................smoked turkey's da BOMB!