Just a few thoughts...I know others have covered some of this.
#1 - I don't spritz or mop or even open my smoker AT ALL, for at LEAST 2-3 hours after the meat goes on. I only open the firebox to stoke the coals and add more wood or lump. Opening the smoker chamber - even if it's just once an hour, can really affect the finished product, I think.
#2 - Temps probes: Best = Maverick ET-73...you will love it, totally worth the investment. I also use the Taylor 1470, but the maverick has a probe for the meat AND a probe that just measures temps at grate level.
#3 - Pork Butts. I cut mine in half every time now. It increases the surface area to which you can apply the rub (more bark...yum!) and it will cut the total cook time from 10 hours to 7 or so...depending on size, of course. Read the "sticky" post here on this forum, in the pork section, about doing pulled pork. Very informative.