Use a couple of probes in the meat, and one "outside" the meat for ambient temp inside the smoker. I discovered that the ambient temp in the smoker was radically off from the smoker's thermometer. I found that I had to run the smoker at a lower temp (190 or so), to achieve a 220 degree ambient inside temp.

TLDR: Get a good digital wireless thermometer with like 4 probes on it. I got mine on Amazon for a few bucks. Well worth it.