I have a WSM 22", and here is what I do:
- full load of charcoal (unless I'm doing a very short cook, but never less than 1/2 full)
If there's leftover briquettes from last time, I shake off the ash and pour fresh on top.
- make a well in the center (usually not all the way down to the grate), and add 10-12
fully-ash-covered coals in the well. Then I place the smoke wood (3-4 chunks) touching
the hot coals, then assemble the smoker.
- top vet fully open throughout. Bottom vents fully open until 150 degrees at the grate,
at which time I close 2 bottom vents fully. At about 200 degrees, I close the third
bottom vent about 3/4 closed, and the grate temp will coast up to anywhere from 220
to 275, depending on temp, sun/clouds, wind, etc. Once it stabilizes, I'll open/close the
one vent to adjust the temp to about where I want. At 220-225, it's not unusual to have
all three bottom vents fully closed (I don't have gaskets, so there's enough leakage
to keep the fire burning)
- once the temp stabilizes, it's rock steady, rarely varying by more than +/-5 5 degrees.
The biggest key for me is to start closing off the vents early, so the fire doesn't build too fast. Once charcoal ignites, it's not going to go out on its own, so once the temp gets too high, it's really hard to get it back down.