We learned this in survival training when I was in the Navy. The Dakota fire hole - conserves wood while minimizing smoke and light from the fire. it also helps cut the light and smoke that can be seen by others or, eh hem, Walkers.
Making an upside down fire. The upside down fire technique rocks. It’s a cleaner burn with far less smoke and better combustion, gives off more heat, needs less tending and uses the embodied energy in wood more efficiently than the tipi-esque fire method.