Smoke is caused by little bits of the burning material which flake off and are carried into the air by the updraft of the flame. More smoke is produced by incomplete combustion, and combustion is helped by having access to more air. If you wanted to produce more smoke from a fire you would try to restrict its access to air such as by covering it with damp branches. To reduce the amount of smoke you would want to increase the fire's access to air, which is done by raising the fire and putting air holes underneath it. This allows it to steadily draw in fresh, cool air which allows the fuel to burn completely instead of becoming smoke particles. A similar technique can be used in the wild to make a stealthy fire. Two holes are dug and connected by an underground tunnel. A fire is built in one of the holes below the level of the ground, which prevents the flames from being seen from a distance. The other hole and tunnel allows fresh air to be drawn in near the base of the fire which again reduces the amount of smoke it produces. Answer from Phage0070 on reddit.com