This is a good question, if you light some charcloth, what do then use to conjur up an actual flame.
Look at tinder in two groups, those that can catch a spark, but not necessarily develop flame (charcloth) and those tinders that can catch spark and eventually , with encouragement, can go directly to a flame, such as the kleenex mentioned, as well as a traditional tinder bundle.
I'll give the canned answer, "it depends where you are".
Doc up in Canada may use fine birch bark shavings or dried grasses. Runningboar in North Carolina may use fat wood shavings.
I'll stick my neck out a little and say that tinder is a regional type of thing.
In general, there are types of tinder that span most of North America, such as dried grasses. You could scrap the edge of your knife along your pants or shirt and get some "fuzz" from your garment. You could find some dry bark, and scrap the inside of it for some natural "fuzz".
I guess my answer is not a great answer, because what I would use may not be available in another part of the world.
The important thing, for each of us, is the question itself, what would WE use, in our corner of the world?
But, back to the specific question, I would use a traditional tinder bundle made of dried grasses, and fine scrapings from the inside of dried bark. It would resemble a bird's nest, and would be made in such a way that I could place the charcloth inside, so it was touching some of the "fines" so they could also catch the sprak, and then be cultivated into a flame, usually by blowing on it.
Once you have blown it up into a flame, hopefully you had the foresight to have a little kindling teepee already built.
