All the above are great suggestions and will get you right on track for your brisket. My personal barometer for doneness is the toothpick test or probe test that HarleySmoker mentioned. I only use the IT for reference points only, in other words, once the brisket reaches 200 to 205, I'll start probing once it reaches 200, then every 5 degrees after that (205, 210 etc.). Most of my competition briskets don't reach probe tender until around 210 to 212 (then they get a 4 hour rest in my warmer box before slicing). Now, this will yield a fall apart tender piece of meat, to make my turn in boxes for comps, I have to use a cake icing knife to pick up the slices, but that's what wins in Texas and it's how I personally like my brisket to be as well. If you prefer a hold together slice, then you might choose to pull it at 200 or 205, then rest for at least an hour or so in a cooler wrapped in towels. This will allow for some carry over cooking along with the redistribution of the juices throughout the meat. The optimum IT prior to slicing for brisket is in the 160 range, in other words, the It must come back down to the 160 range before slicing to prevent your cutting board from having more juices on it than is in the meat.
Good luck with your brisket, but most of all have fun!