The triangle of fire.

Fire needs 3 things - fuel, air and heat. Take one away and the fire will go out. Don't provide one and it won't even light. Wet wood absorbs heat and so will cool a fire. You can smother a fire with too much fuel. And if you haven't a heat source such as a flint and steel then it'll just sit there staring at you whilst you freeze.

The tree of fire

Silver birch is the best tree. Its quick growing and Its bark is great for fire. The bark if peeled acts as a natural fire lighter but don't take more than you can peel, using a knife can make tree is more prone to disease. The ends of the branches give lots of fine twigs which is wonderful kindling - don't take these off the tree, there will be lots of wind damage twigs beneath them that are dry. Seasoned birch burns magnificently but you'll not find that in a wood without significant planning or unless its fallen and got lodged off the ground. Birch left on the ground rots quickly and soaks up water like a sponge - great for woodlice but poor for firewood.