My grandfather has smoked a turkey on the kettle for 40 years. He uses the method for indirect cooking described in the manual that come with a Weber kettle. Start with 25 lit coals per side and add 8 unlit coals per side each hour. We also add some wood chips throughout the cool when adding coals. This is using original Kingsford Blue Bag. It takes 11-12 minutes per pound using this method, though now that I have my Thermapen I suspect that may be a little overkill. I also prefer a different, cleaner burning coal than KBB but I'm not willing to fight my 85 year old grandfather on either!
I would set up a drip pan but NOT fill it with water. You will want your temps 325 (definitely above 300) or the skin will not crisp up and rubbery poultry skin is gross. Water is a huge heat sink that will keep your temps lower and also create a more moist environment that isn't conducive to crisping the skin.
There are definitely other methods to smoke a turkey but I can say that this has worked for 40 years and it's all I've ever had on Thanksgiving in my 28 years.
I will be messing around wlth some other techniques for the Thanksgiving turkey throw down.