Fire control, fire control, and then FIRE control...
That, and I'm still amazed how many here dont know that the temperature shown on your external mounted thermometer (the one you can walk up to the smoker and read) is likely to be 20 to 50 degrees OFF from your actual cooking surface temperature. When we talk about cooking temperatures, it's on the cooking surface itself. I cannot tell you how many pieces of meat I ruined before I learned this simple lesson and that I'd been trying to cook meat (unsuccessfully mind you) at 180 degrees rather than the 220 showing on the thermometer. AND that this doesn't mean that the thermometer is broken or wrong. Darned if heat doesn't do this funny thing; it rises. In my case my thermometer was towards the top, where heat accumulates...
Afterwards, work on fire control.
Hance - Lake Dogs Cooking Team - MiM/MBN/GBA CBJ and comp cook
Lake Sinclair, GA (strategically about an hour from darn near anywhere)
Started competing in chili cookoffs back in the 1990's and have competed in more than I care to count. I became a CBJ in MiM in 2005, then MBN and in GBA in 2010. I've probably judged 130+- BBQ comps (sanctioned and unsanctioned) over this time. That said, I really enjoy competing more than I enjoy judging, and hope to get back to doing 4 or 5 a year in the near future.