I smoke a few turkeys each year and just smoke a 20 lb bird this last weekend.
-Brine the bird - the smoke flavor is enhanced, the turkey ends up juicier, and it supposedly keeps better afterward
- Inject if you want to add some additional flavors. My hands down favorite is to inject apricot brandy in the breast and thighs. rub down with some olive oil and a few spices, throw some sweet onions and a split up apple in the cavity, but leave room for air and smoke to pass through. Simple and it comes out great
- Smoke setting is usually 225-235. I use two thermometers as I like to get the breast to about 167 F and the thighs to about 180 - Time varies by smoker: My bullet smoker if I keep at 225-235 will take about 10 hours for a 20 lbs bird. My pellet smoker just took 7 hours when set at 225-230. This is one of those smoking mysteries that I will probably never figure out.
Did track the temperature on this last turkey I did on my pellet smoker - at 225 - 235 degrees, the temp in the breast increased by about 20 degrees per hour for the first 5 hours, hour 6 was only 13 degrees, and hour 7 was about 9 degrees.
Do not tie the legs together when you put the turkey on, just wrap a little foil on the end of each leg (about 2 inches) and let the leg hang free. This will let more heat get to the thighs and legs which will help you get the temp up on those.
If you are not into the crispy skin on your turkey the above works great. We usually throw away the skin or give to the dog when we carve our turkey anyway.