Everyone forgot to mention charcloth. Pretty much take some cotton (ie, old t-shirt), wrap tightly in tin foil, throw on some coals for a few minutes (BBQ, campfire, whatever). When it starts smoking it's done. Let it cool. The cotton should be singed - should take a spark easily.

Also, birch is great. Youtube it, but you take the bark, flip it over (so the outer surface is on the ground) and use your knife to scrape it and make a pile of powder. Those shavings go up in a heartbeat. It then catches the rest of the bark on fire, which you move to your already-set-up fire.

Pretty much like everyone else, has to be dry, has to be fine. I can't get cattails or grasses, and only a few types of bark to go up. Using any vaseline is cheating, but works.

Personal opinion, but ditch the magnesium block. It's a POS, and I've NEVER gotten mag shavings to be helpful. Using a file to get shavings is better than chewing up your blade, but still ... the return is so low it's almost laughable.