The technique of indirect cooking is essentially a slow roasting process which guarantees a tender result. When you think about it it's pretty logical. The definition of indirect cooking is where the heat is not directly applied to the turkey as opposed to a grill where the turkey is seared directly over the charcoal barbecue grill.
In my house it's always down to me to cook the turkey for Thanksgiving or Christmas and every year I read a bucket load of recipe books and everyone says something different. My biggest complaint is that most of the voices of authority for traditional cooking out there always overdo it and the breast is dry however there is a way to keep the turkey moist and this is why I go for indirect cooking on a barbecue smoker. If a direct barbecue grill is however your thing then you'll be better going for turkey grill recipes and choose some sliced breast.
Don't be tempted to go overboard looking for additional flavourings, the smoker will impart all the flavour you need so there's not much more to add than the basic seasoning, the real challenge is to keep the turkey moist through the cooking process. If you, go for a relatively small bird around 9 - 12 lbs (5 or 6kg) you'll make life easier for yourself, after that, try my two tips:-
Melt 100g / 4 oz of butter in a pot and add a tablespoon of oil - this baste will give all the flavour of the butter without burning it. In addition I like to part the skin from the flesh by gently sliding my hand up from the neck and smear some butter up there but if you do fancy trying this, do be gentle so that you don't break the skin.
The second technique I use is to inject the turkey with the butter / oil mix. Use a meat injector (essentially a syringe with a metal capillary attached - as opposed to a needle), gently suck up the butter oil mix and then inject it carefully into the breast. Then it's just a matter of seasoning with salt and pepper and basting and then place breast side up on the BBQ smoker.
You may be able to get away with a large kettle barbecue but essentially an offset smoker or a kamado barbecue such as a Big Green Egg is ideal. After that is just medium coals and indirect heat @ 225°F or 110°C, a drip tray in the bottom with a couple of tablespoons of water and you're well on the way. It may be necessary to use foil to shield the sides but that really depends on your barbecue. Just cover and baste every 30 minutes or so with the butter / oil mix and 3½ hours later you should have the perfect Thanksgiving barbecue turkey.
The best test for me is not how long it's been cooked but a skewer test for clear running juice in the breast and legs or a thermometer and look for an internal temperature of 165 °F. If it's not quite ready just give it another 30 minutes and a baste and try again.