Fire needs three things: heat, fuel, and oxygen. Zoom in on a simple match: when struck, friction applies heat to a chemical fuel that ignites in the presence of oxygen––a reaction visible as flame.
A fire in a wood stove or fireplace follows the same principles, but has more moving parts, and thus requires the kind of methodical poking and feeding that calm the mind. Maybe this is why they are so universally therapeutic. (No one has ever sat back and relaxed in front of a match.)
You’ve built a fire; now, keeping the triangle in mind, you have a conversation with it: feeding, correcting, watching. Keep it fueled. Once going, it will provide its own heat from flame or a coal bed. Help it breathe by providing space for air to draw up through the fire, especially when you add wood.
Smoke is uncombusted carbon and indicates insufficient heat or oxygen to maintain a flame. Poke it. Adjust the wood closer together if it needs heat; break it apart a bit if it needs air.
Though the fire-maker wants very much to build a “perfect fire,” this is not unlike the golfer’s longing for the perfect game: while theoretically possible, it is quite unlikely in a lifetime of practice. The fire-maker like the golfer must derive his or her satisfaction from the pursuit.