Trim the fat cap to about 1/4" and remove any large deposits of fat or hard spots of fat. Slather the butt all over with yellow mustard and let it sit for about 15 minutes, then apply your favorite rub. I would suggest that you purchase Jeff's recipes for rubs and sauce. They are very user friendly and can be tweaked to your personal taste without changing the basic quality. The proceeds from the recipes go to support and maintenance of this great site.
I usually smoke a butt at 250-275*. When the IT gets to 150-160*, the cook will stall. When the stall sets in, double wrap the butt in foil. Add 1/2 cup of apple juice to the foil. The apple juice will help with flavor and moisture and the acidity will help with tenderness. When the IT reaches 205*, open the foil and see if the bone pulls easily from the butt. If it does, the butt is ready to pull. Wrap the foiled butt in towels or a blanket and put in a dry cooler to rest for an hour to let the juices redistribute back into the butt.
The butt is now ready to pull. Pour any remaining juices into a bowl to mix with your finishing sauce. Take out any fat that you can see and shred the meat and bark. A good finishing sauce is your remaining juices mixed with 1 cup of apple cider vinegar, 3 Tbs. Brown Sugar, 1 TBS Kosher Salt and 1 tsp. Red pepper flakes. Use this sauce sparingly. You're not trying to flavor the meat, only add a little moisture. You should now have a good tasty pulled pork meal.
If you want sliced butt instead of pulled, change the finishing IT from 205 to 185*
I hope this has not too long, but you asked..... Good luck with it. Let me know how it works, Joe