Jon has the right idea, I have cooked hundreds of them in my day, (not all at one time of course!) The brisket is a very tough cut of meat, and to be tender it MUST be cooked very slowly. I use packer trimmed brisket and cut off all the fat except for about 1/4 inch, use a dry rub of equal parts garlic powder chili powder salt and pepper, an let set if the frig overnight. Bring the meat to room temp while you are preparing the cooker. I use both an offset firebox type and a water smoker. Get the cooker temp to 120 - 130 deg., place the meat on fat side up for about 1 hr/lb don't turn the meat. I use chunks of either Hickory or Mesquite. Remove when the internal temp hits 170 - 180, wrap in foil and an old towel and put in a foam type container to keep until serving. You can experiment with the finished temp. depending on how long you need to hold it before serving. When slicing always slice across the grain of the meat.
Good Luck!