Beef brisket is a very popular cut of meat to cook in pellet grills/smokers as it can take many hours to cook. Hence, the fact you don't have to babysit the brisket on a pellet BBQ is appealing to a lot of people.

You'll want to start by trimming the brisket of excess fat, making sure the fat is down to a quarter of an inch. In terms of brisket prep there are many options (recipe links below). 

In terms of smoking the brisket, to get the most smoke flavor into it you'll typically want to start with the pellet grill running at 225 degrees with either Hickory or Mesquite pellets.

Smoke the brisket up to an internal temperature of 165 then take it off, wrap it in foil, and place it back on the pellet grill until its internal temperature is 200 degrees. During the wrapping stage, you can increase the temperature of the pellet grill as its no longer in the smoking stage, its being braised.

Once the wrapped brisket has reached an internal temperature of 200 degrees, take it off the grill/smoker and leave it to rest for at least an hour before you cut into it.

Now, my comments above are obviously just highlights of the process, and there are lots of different approaches to smoking a brisket. Below are links to just a couple of brisket recipes.

Brisket Recipe 1

Brisket Recipe 2

Brisket Recipe 3

Brisket Recipe 4