Get rid of that disposable lighter! Strike a spark and breathe it into life as was done in early times. With good materials and a bit of practice, fire making with flint and steel is quick and reliable.
When you strike a spark, you are shaving tiny pieces off the steel with the sharp edge of the flint. The pieces become incandescent from the friction. The sparks come from the steel, not the flint. The harder the steel, the smaller, and hotter, the pieces will be. The sharper the flint, the more sparks you will get. Strike down the steel with the flint at a shallow angle. Point the steel into your tinderbox to direct the sparks into your tinder. Learn to use short, choppy strokes so you can hold the steel close to the tinder without hitting the tinder with the flint. Keep your fingers back from the edge of the steel so you don't cut yourself with the sharp flint. When your flint becomes dull, chip it back to a new, sharp edge. Keeping the edge of the flint at a very shallow angle to the steel will increase the useful life of the edge.
You can also use many other minerals as your "flint". Agate, carnelian, jade, bloodstone, chalcedony, quartz, and chert all work well. Any hard stone, which fractures to a sharp edge, will do the job. Keep your striker with you, and when you see an interesting stone, try it.
You will need some prepared tinder. This can be almost any natural vegetable fiber. Cotton, linen, jute (burlap), sisal, hemp, or weeds from the field all work. A mixture of two fibers usually kindles more easily than any one fiber. Cotton and jute is an excellent combination. A wad about the size of your fist should work well. It is best shredded fine and well mixed. When I was a boy it was common to use dryer lint. This worked really well at the time, but can no longer be recommended. With modern synthetics, dryer lint is likely to contain at least some polyester or other plastic. The fumes from many modern synthetics are TOXIC. Holding a wad of smoldering tinder under your face and taking deep breaths to blow hard is a BAD THING if there is any plastic in the wad.
Only partly burned fiber catches a spark easily. Add new tinder as needed to the bottom of your tinder box so the top surface is charred from previous uses. You can greatly increase the speed and ease of your fire starting by using prepared "char-cloth". To do this, place some cotton or linen cloth in a tin with a loosely fitting lid. Hold the tin over a flame. As the cloth chars smoke will come out of the tin. When it stops smoking, the cloth is done. Set the tin aside to cool before opening. If you place a layer of the charred cloth on top of your tinder, it makes a large target for your sparks. This really speeds the process, but I haven't been able to document the use of prepared char-cloth (in the sense of cloth heated in an airless tin, as opposed to just using partly burned materials) prior to 1910 or so (Boy Scout movement). In the early periods cloth was precious, not to be wasted on fire starting. Even rags were useful in household chores, or for the cauking of boats. In the American colonial period tow was often used. Tow is the fiber of the flax plant (linen) before it is spun into thread. Cotton balls work well also. Various types of fungus were commonly used from the earliest periods. I’ve seen reports of late stone age fire starting kits with iron pyrites, fungus and coarse tinder. From the early medieval period until the invention of the match a treated fungus product called amadou was widely used to speed the process.
There are two basic ways of starting a fire with flint and steel. In the first, which I call the Boy Scout method, you hold the steel in your left hand (assuming you are right handed), and strike the steel with the flint held in the right hand to direct sparks into your tinder box or wad of tinder. To make fire, lay a scrap of char-cloth on your tinder. Strike sparks into the tinder until it glows. Fold the tinder around the glowing ember and gently blow on it. As the glow spreads, blow harder. If your tinder is dry, it will quickly burst into flame. With good materials, the whole process takes only 10 or 15 seconds. Transfer the flame to your candle (or whatever) and smother the tinder in your box for the next time. When used with char cloth, this is much the quicker method. When used with tinder that has simply been partly burned it can be rather slow, because catching an ember depends on a spark striking a surface that is chared.
In the second method, which I call the traditional method, you hold the striker in the right hand. In the left you hold a shard of flint with a bit of chared material on the back of the flint just behind the edge. When you strike the flint hot sparks should skate into the peice of char causing an ember. Then you transfer the ember to your tinder and proceed as above. This is just a bit slower since you have to transfer the ember to the tinder, but it is more certain if your materials are marginal. The spark doesn't have to travel as far, and is likely to burn hotter and longer in the char or tinder.
I expect both methods were used. I've seen a description of firestarting in a handbook for house servants from the early 1800's. It describes the first method, where sparks are struck into a tinder box. Evidently char cloth was not used, since the manual states that a "common serving girl" should be able to produce flame within twenty minutes. The second method was probably more common however. It works much better with small pieces of char, amadou or tinder tubes (see below). Also some period tinder boxes had the sriker built into the edge of the box, so it would have been impossible to use it to strike sparks into the box.
If you smoke, or shoot a matchlock musket, you don't need an actual flame for a light, only an ember. In this case you may find a tinder tube to be handier. This is a tube an inch or two long, 1/4" to 1/2" in diameter, with a length of cotton rope inserted. The end in the tube is charred. To get a light, push an inch or so of the charred end out of the tube. Hold the charred end on top of your flint near the edge. Strike down the edge to skate a spark into the charred end. Blow gently to spread the ember over the surface of the rope end. After lighting your pipe, snuff by pulling the end back into the tube and closing the end with your thumb. Be careful not to rub off the char, or it will be difficult to get a spark to catch the next time. The whole point of the tube is to protect the char. Period tubes sometimes had a cap for the end of the tube. A piece of wire shaped like a fish hook was attached to the cap. The hook was inserted into the cotton rope, and was used to pull out the charred end. After use, the rope was pulled back to draw the cap tight and smother the ember. This was the period pocket lighter, and the best examples were finely made of precious materials such as silver or even gold. In more modern times the tube was updated with the addtion of cigaratte lighter type wheel and flint to produce the spark. During WW I and II they were used in the trenches because they didn't produce a flame to draw sniper fire. In the rural parts of Spain they are still in use, and are called Shepherd's lighters.
A tinder tube is much handier than loose tinder, but does not produce an actual flame. Of course you can always transfer the ember to your tinder, and puff it into flame. I've been told that it's possible to light a candle with one, but I've never managed it myself.
Recently there as been increased interest in using the back of a knife blade as a firesteel. This has been sparked by some books on wilderness survival recommending the method. I’ve had limited luck with it. To get a spark, the slivers of steel must be small enough to become incandescent from the friction. Most knives are not hard enough, and the pieces gouged out are too large to become hot enough to form a spark. In my experience you need a minimum of about 60 on the Rockwell scale to get sparks with the methods described above. Even then you will have to work at it. The most common knives that are this hard are the carbon steel Mora knives. Stainless steel blades of any hardness do not seem to work.
If you are using the softer steel found in most knife blades, you can still get a spark by holding the edge of the flint at more of a right angle to the steel, so as to scrape rather than carve off pieces. This reduces the size of the pieces and increases your chance of getting a spark. It requires more force, and is hard on both the flint and the knife, but it does often work. You won’t get as many sparks as you would with a real firesteel, but you only need one spark in the right place to get your fire.
Since you will be getting fewer sparks you may find it better to strike the steel against the flint as mentioned above. This improves your chance if getting a spark into the char. The downside is that you need to be very careful not to cut yourself in the process. This isn't a problem if you are using a folder. Just keep the blade folded into the handle while you are striking.
Striking the back of the blade with the flint is less efficient but much safer. Hold the knife at an angle with the point in a wood surface and the tinder under the blade. This stabilizes the blade for a firm strike.
If you need a striker, you might want to look at the catalog page.