Friction
Use a little friction and some effort to build a bonfire. This method is difficult, requiring a high degree of personal effort and patience. Building a tinder nest, using grass, dried refuse and bark. With a knife, cut a "V" into a small piece of wood to give the spindle a notch in which to rest. Place the notched board atop the tinder nest, to catch the sparks. Hold a 2-foot, thin, spindle-style stick between your palms and place it in the V notch. Vigorously roll the spindle between your hands, moving them up and down the spindle to maintain a downward pressure. Once a spark occurs, tap it off the board and onto the tinder.
Modern Method
A more modern approach is to use small pieces of kindling and arrange in a teepee structure, with a small amount of tinder placed underneath the structure. Use a match or lighter on a piece of paper or dried tinder; once lit, place it underneath the structure. Alternatively, drop a lit match inside the teepee structure. Use dried logs to build a "cabin" around the outer edges of the teepee.
Flint and Steel
Natural or synthetic flints can be purchased from most camping stores -- often with a small piece of steel that is used as a striker. This is a standard survival item to pack before heading out on the trail, as matches can get wet and lighters can be unpredictable. Place tinder as you would for other methods. Grasp the back of the steel striker and strike it against the flint several times, holding it directly over the tinder. Continue until sparks from the steel fly off and land on the tinder. Once you have a glow, begin to add fuel to the fire.
Focused Sunlight
Use a lens from an old pair of eye glasses, binoculars or a magnifying glass. Place the tinder on the ground and hold the lens directly overhead. Angle the lens so that is directs the sun's rays; make the smallest focal point possible. When the tinder begins to smoke, blow gently until the fire ignites. If you do not have a lens, try using a clear balloon, condom or rubber glove filled with water to create a makeshift lens. This method works only when there is sufficient sunshine.