Drawing resistance
Drawing resistance is critical to a good smoking experience. If the resistance is too high, you will need to draw heavily. This will make the pipe overheat faster and more condensate will form, which often makes new pipe smokers draw even more hastily.
This indicates the tobacco is tamped down too strongly.
If the filling burns easily but the tobacco fails to glow despite an appropriate moisture content and soon goes out, it is likely that the tobacco was tamped too loosely.