After I get the pipe lit and smoking well, I usually give the bowl a tamp or two as the ember burns down into the bowl. This is to gently push the tobacco into closer contact with the ember. The fire needs fuel to continue to burn. I also ash my pipe, which is to gently poke the soft ash to loosen it and dump it out. When your smoke seems to get tasteless try dumping the ash. Water is a combustion product, and the tobacco in the bottom of the bowl will get more moist than it went in, and can get wet enough to not burn very well. That moist tobacco in the bottom of your bowl is the dottle. In a cob, I may get no dottle at all because the cob is absorbing the moisture. In a big deep briar like the ones I like to smoke from I may get a lot of dottle. I can try to coax a few more puffs out of that dottle, but I usually toss it. If the dottle is a nice plug of moderately charred and unburned tobacco, I dump it into a bowl where it can dry out and get smoked later.
