In my opinion, the most common factor of a burnt tongue and mouth is improper drying of the tobacco before smoking, thus causing the smoker to puff more quickly in an attempt to keep the moist tobacco lit. This excessive puffing creates hot steam, which burns the tongue and mouth. The dryer the tobacco (to a certain point), the slower one can puff and the cooler it burns. Most low quality aromatics like Captain Black are heavily cased with PG and will never properly dry out. Unless you have a leather tongue, it might be best to avoid these.
The second most common factor in my opinion is packing the bowl too tightly. Gravity filled with a very light tamp seems to work well for many smokers.
As others have already mentioned, there are also other factors. For some reason, I cannot smoke MacBaren blends. They always burn the hell out of my mouth- even when properly dried. I'm guessing it's a body chemistry thing (due to the Virginias they use?). It's a shame, too, because I really like their Vanilla Cream and Virginia No.1 blends.
