I'll usually pick up things while out walking that'd make good tinder if I'm going to make a fire later. Dead pine needles, dry grass, wood shavings I whittle with a SAK, certain types of hairy moss....things of that nature. I'll gather these easily ignited substances into a small pile with a good sized stick poking up out of the ground in the middle. Lay tiny sticks of wood tipi style around the tinder, leaning on that support stick in the middle. Once things catch, just throw on slightly bigger sticks and work your way up. Real simple.