A saw is a helpful tool for cutting firewood, sawing tree limbs or clearing a tree that has fallen across a trail.
When sawing for firewood, brace the piece of wood against some kind of solid support and cut with long, smooth strokes. Let the weight of the saw pull the blade into the wood.
Just like your pocketknife, you should take good care of a saw. Protect the blade with a sheath. You can actually make one yourself by cutting open an old garden hose and fitting it over the blade. When the blade gets too dull, just replace it.