Your blood is still safely inside you. You have a bottle of filtered puddle water nearby. You have a makeshift lean-to/tent to keep the wind off your head. The pile of branches protecting you from the cold ground is uncomfortable, but you are getting used to it.
Then you shiver. You’re going to need some sort of chemical reaction that combines heat, fuel and oxygen. A fire.
Tinder
Some of today’s more interesting phone apps won’t help you, for the record. I’m talking about little bits of paper and flammable bits of tinder; put your damn phone away, this is the apocalypse remember?
Tinder is essential as your first step towards fire. The requirements for good tinder are as follows: high surface area (tiny pieces count), low moisture and ease of gathering.
Some options include dry tree bark (birch specifically), pine needles, fluff from cattails, wood shavings or sawdust, newspaper, or any other sort of paper. Lots to choose from, if it's light, fluffy, paper or in pieces… try it out.
Ignition
Just staring at tinder won’t get you anywhere, you need something to light the fire. If all is going well just pull out that trusty Bic lighter and getting to burning some stuff up. There are a number of tools and methods to use to start your fire, far too many to list here, but check out some of our links for more information. Let’s assume you have a regular old Bic lighter for the sake of any arguments.
Fuel
After tinder comes kindling, still small but slightly larger and helping to maintain a stronger and longer lasting fire. Pine cones are great, but the best kindling is 6 to 12-inch-long pieces of “roughed up” wood. Either a little splintery on the edges or having been prepared by a knife by curling some of the edges of the wood.
After kindling comes logs. Once you get to this point and the logs are burning, your fire is going to last a long time. The only concern you should watch for? Using dried dead wood can make the wood burn faster than you’d like.
Portability
This may confuse you a bit, but let me explain. If you must move an established camp, being able to take your fire or at least some embers with you takes hours off the time needed to set up the new camp. There are some tried and true methods available in history (here’s a wiki article on fire pots), mostly falling under the category of Fire Pots. The common threads in a fire pot are airflow, but not wind, and being made of a non-flammable material.
A few pieces of embers and charcoal from the bottom of a campfire stuck into a tin can and carried safely along with you could be enough to restart a fire later that night.
Maintenance
Maintaining your fire can be the same as maintaining your only means of survival in some climates. How you lay out your initial fire can have a great bearing on how quickly the fuel burns and how much fuel you need for it burn as long as you need it to. (check the second link below, the section titled "2.5 Wood Stacking Designs")
The main three things needed to keep your fire going are Oxygen, Heat and Fuel. Fuel is kind of obvious, keep adding more wood. Heat can be tricky, actually; if you are down to embers, there may not be enough heat to continue burning at the levels you need.
Lastly, Oxygen. This will only really be a problem if you choose to build your fire in a pit like the Dakota Fire Hole design. But it is a concern, if you smother the fire and oxygen can’t get at it, it’s done.
Safety
Before all that stuff up there, you need to check out your area. Since I didn’t write this in proper order, you’ll have to check it now. Make sure nothing is overhead, and plan your fire’s shape and size as best you can for your skill level.
If you can, have some way to smother the fire quickly. Dirt or water work best, and a large enough quantity of salt can also work, but salt has much better other uses in a survival situation. In any case, have some way to put it out if you need to. Don’t skip this step, it's likely the most important one.
After the fire goes out, remember to cover your fire pit with dirt or otherwise ensure it is out for good. This is also very important; a lot of forest fires are assumed to be caused by some well-meaning hiker starting a fire and forgetting this step.
Creative Fire-starting
There are quite a few non-standard ways to fire up a heat source for yourself. Here's a link so you can go look at what I found, some of them are awesome! (not a sponsor, it's just neat!)
My personal favourite is a 9V battery and steel wool. I’ve already put it in my camping bag as an extra method.
The Standard Warning
We cannot stress enough to receive proper training and to do your own research regarding these topics. Although this information and these facts are as accurate as we can relate them, we are not recommending nor are we suggesting in anyway that you use anything but properly sourced and prescribed medicines, materials and methods.