Note that the title of this article is not "How To Light A Fire." That is a much more complex subject. This article assumes you can produce spark or flame and is concerned with helping you turn it into a blaze.
So you've seen the cartoon. A careless camper doesn't completely put out his campfire and a small spark starts dancing around setting the world on fire. And in one of life's little ironies, its true. A small spark or even just an ember, can start a conflagration to rival some of the outer layers of Hell. I've seen it. I've done it. My neighbors were not amused. Neither was the fire department, state foresters or the judge, who already knew me by name. We've all moved on now and there is no point living in the past, but it is ironic that massive fires can happen so easily on accident but can be so hard to start deliberately.
On paper the secret to fire is pretty simple; apply the right amount of heat to the right amount of fuel and presto, the foundation of society is ignited. The wolves are kept at bay, hypothermia is staved off and the elk you took down with the bow you made yourself is roasting on a spit to a barely warm medium rare. Or just as likely, your lovingly constructed mini-tower of wood and combustible materials is simply smoldering impotently and maddeningly as the cave women awkwardly try to avoid making eye contact with you. Get your rocks back out Ally Oop, we're starting over.
If you are a theoretical type and need to know the hows and whys of something, then a brief but informative description of how a fire works can be found here. If you're more of a doer then just keep reading.
So you've gathered some wood of varying sizes, but do you have the right kind of wood? What's that you ask, you thought all wood burned? Well yes but does it burn readily? I sold a load of firewood to a guy one time that he couldn't get to light with a natural gas fire starter. The log had been on the ground for years when I cut it. I couldn't get it to light and I am a certified Fire King. The stuff was damn near fire-proof. I would throw one piece on a fire at the end of the night and it would still be burning in the morning. I got to looking at it and I couldn't even tell what kind of wood it was. The farmer whose land I cut it off of thought it might be something called black gum but he wasn't sure. To this day I've never run across it again but it took me an entire winter to burn off that wood. My point is this, that there are types of wood that will burn almost magically (think fatwood, long dead pieces with large concentrates of dried sap) and some that won't burn hardly at all; like my mythical black gum tree that even the farmer admitted he had only heard of and never seen.
Black gum aside, most woods will burn with reasonable readiness if they are both dry and dried. What's that you say? How does one dry a dried wood and does that mean wood can be wet and wetted? Of course not, that would be silly. It would be green and wet in that case. Your options are dry dried wood, wet dried wood, wet green wood and dry green wood. You can almost never have dried green wood. Dried is better than dry but obviously dry dried is far better than wet dried but in most cases wet dried is better than most dry green. Wet green is a recipe for a raw dinner and a cold night. If all this seems a little confusing read this but the short of it is that you want wood that has been dead for a while.
A good rule for choosing the wood to start your fire is that lighter woods (that is woods that actually feel like they don't have much weight, there's no trick vocabulary in this instance) are easier to light on fire. Also, they don't burn as long or put off as much heat so its doubly beneficial to use these to start your fire. Some examples are pine and poplar. Both are light and easily combustible. Pine will break this rule if green but poplar (which is always green, its the natural color of the wood just to confuse that issue a little more) will light readily most of the time and has the added benefit of a fibrous bark that provides wonderful tinder when paper and dried grass is unavailable.
Now you're probably wanting to dig a pit to put your fire in, after all safety first right. Well take that desire and bury it in the pit you've dug. Its not that safety isn't important. Its not that you can't start a fire in a pit. Its just that it can be very hard to start a fire in a pit and if you are really so worried about safety that you will risk not starting a fire then you probably don't really need or want the fire. Get out your George Foreman grill and be safe and eat less fat you metrosexual twinky. If you are that worried about it, build a ring of rocks. Pits block air, sap off heat and are usually damp; all things that will inhibit your fire. If you need an explanation of this then read the brief but informative description of how a fire works that you obviously skipped earlier.
Alright, so at this point you should be ready to start building a fire. And that's what you have to do, you have to build a fire from the ground up. The foundation of a fire is the tinder. This is the easily combustible material that you will apply the spark to. In the civilized world this is frequently paper. In the wild it can be any number of things, but is frequently the part where most fires fail, so let's talk about tinder.
Tinder has to be small, it has to be dry and there needs to be a lot of it. The best is the fibrous inner layer of bark. Not every tree has appreciable amounts of this fiber and in most live trees this fiber holds a lot of moisture, rendering it useless as tinder. Two kinds of trees to always keep an eye out for when starting fires are poplar and cedar. Dried examples of these barks have large amounts of easily shredded fiber that are fantastic for starting fires. Other things that can be used for tinder are dried grass, dried moss or extremely small slivers of wood, think smaller than toothpicks. Now let me reemphasize that there needs to be a lot of tinder.
Now there are as many types of fire starting structures as there are fire starting people. Most of them can be effective, even the ridiculous teepee method that seems to have been invented solely to frustrate Boy Scout troop leaders and give cartoonists easy ways to draw fires. The best way I've found is to lay two largish pieces of firewood on the ground perpendicular to each other. Pile your tinder on the ground between the two pieces of wood. If the ground is damp then lay down a few sticks to keep the tinder off the ground and from absorbing the moisture. Now lay two pieces of wood across the base pieces of firewood so that you have a ladder like structure when viewed from above. These crosspieces should be smaller, think the width and thickness of your thumb. The tinder should touch the bottom of the crosspieces and extend past them significantly along the length of the structure. Now layer small pieces of wood on top of the cross members, these would be very small slivers and flakes. These layers should alternate the direction they run in. As the layers build up the pieces you use should increase in size until they equal the size of the base pieces.
And so there it is, apply a spark to the tinder and stand back and watch the light dance in the cave ladies' eyes. Of course it sounds easy on paper but the certainly any wise primitive staking his life, reputation and the survival of his genetic material on the ability to start a fire should practice a little first. The trick is to always have plenty of dry tinder and small, dry and dried pieces of wood.