Beef brisket is probably the toughest thing to smoke and get perfect of anything that is commonly done. I've smoked them quite often, but even I mess them up a little at times. The reason is that its so easy to overcook parts of the brisket so the beef comes out tough, which is easy to do with such a big chunk of meat, and because of the ton of connective tissue within it. Pork shoulder is forgiving and if you get it a little wrong it still tastes good. Brisket is not.
Brisket comes from the cow's breast/chest area below the shoulder clog/Chuck. It is made up of two portions, the flat and the point. Between the two is a membrane that you could see from the under side. Together they can get heavy, 15lbs or so. At most grocery stores, you'll find the flat sold around 6-8 lbs, and simply called "brisket". The flat has a noticeable grain running along the meat and has to be cut across that grain when serving, or even a well cooked one can be tougher than it should be. The point is a fattier, more marbled side that is used for "burnt ends". The grain in the point can go every which way, so its common to chop this up or cube it instead of cutting strips. The point will have a much thicker fat cap than the flat.
Trimming: No matter how big a piece you cook, there will be excess fat that you want to trim. The goal will be to get the rub to penetrate the meat a little more, and it won't get to the meat through any silver skin or big hunks of fat. The catch is that you have to leave the fat cap or the meat will be dry.
On one side of the point there is usually a very large hunk of gristled fat. Just go ahead and carve that off if the butcher didn't. Next, trim the brisket's fat cap down to 1/4", along with any other obvious hunks that the butcher may have left on. You can do things with it if you so choose, especially grinding and mixing with venison, but I throw it away.
Wood: 1/3 Mesquite, 2/3 Hickory
5 tblsp Paprika
3 tblsp Kosher Salt
2 tblsp black pepper
2 tblsp Onion Powder
2 tblsp Garlic Powder
1 tblsp Parsley
2 tsp Cayenne pepper
2 tsp Cumin
1 tsp coriander
1 tsp dried oregano
1 tsp chili powder
After trimming, apply the rub to the meat as evenly as possible, and don't be afraid to go heavy. The above amounts did the job for a single 17lb brisket. I leave the meat in the fridge overnight or let it sit at room temperature for 30 minutes before going into the smoker.
Build a fire and get the smoker to 225F. Place the brisket fat side up on the grate, and don't touch it for 6-7 hours. You're waiting for an internal temperature of 160-170F. All you should need to do is add wood chunks to the fire about once per 1.5hrs. At the 6-7 hour point, assuming you held the temperature around 225 the whole time, the meat should be getting to that temperature.
When big meats reaches these temps they tend to hit a wall, and will stay there for many hours. Most people panic when the meat reaches 160 and doesn't move for 3 hours, and raise the cooker temperature. This is a no-no that beginners do often. The meat is still cooking and the connective tissues are breaking down at the wall.
Now there are two choices you can make. You can leave the meat unwrapped and take the risk of overcooking pieces around the edges, or you can wrap it in foil. The bark around the outside of the brisket is the main thing affected by the choice, as well as the possibility of oversmoking. I want mine to be juicy, so I take the meat out and wrap it. Most competition brisket gets wrapped.
Then leave it in the smoker, still at 225, until the point reaches an internal temp of 190-200. The flat will reach 200 first, but do not panic, so long as its wrapped it'll be juicy. This brisket took about 14 hours total cooktime, and rested an hour before slicing. It was juicy from the first bite to the last and probably the most tender one I've ever smoked.