Choosing The Meat
Buy a packer-style brisket. It should have a lot of fat on one side, and contain both the flat and the point. It will look like a hill on one side.
Markets will sell trimmed briskets or just the point or flat of a brisket. You don't want these unless you're making other types of finished meats that use the brisket cut.
Buy USDA Prime if you can, but at least get USDA Choice. Here's what to look for: