When I am teaching how to build/make a fire, I tell people to look at and think about the branch of a tree.
We will use this fallen Birch as our example.
For the first stage you need very fine material equivalent to that found at the very tips of the branches.
Next you want material about double the diameter
Now we move halfway back along the branch for rather thicker material which I would consider to be fuel
Once material of this size is burning we are ready to use fuel material closer to the base of the branch
Finally we can now burn fuel of the diameter found at the base of the branch where it joins the trunk.
I am not of course suggesting that there needs to be a convenient branch available each time you make a fire, but looking at a branch gives you a guide to the size of material needed. For a brew fire you would probably only need material up to the size featured in picture three.
In the next post I will put these steps into practise.