Create a pile of tinder, such as small twigs, dried grass or lint.
Angle the magnifying glass so that sunlight is flowing through the glass and onto the pile of tinder.
Blow on the tinder once it begins to smoke to encourage the flame to form. This method takes time, so be patient.
Create a pile of tinder and use a small knife to scrape a pile of magnesium shavings onto the top. You can purchase a small stick of magnesium at any camping supply store. Some sticks even come attached to a key chain for easy transport. One magnesium fire start stick should provide enough shavings to start dozens of fires.
Strike the flint against a rock over the pile until a flame begins to ignite.
Pick up the tinder and hold it in your hands once it begins to smoke. Blow on it gently to encourage the flame to grow. Be careful when holding tinder in your hands and do not let the fire touch any part of your body. Once the flame appears to be growing on its own, put the tinder down onto your pile of wood.
Find a straight stick and a piece of flat bark or wood. Try to find pieces that are as dry as possible. Cottonwood, juniper, cedar and cypress woods will work well for this method.
Cut a V-shaped notch into the board with your knife. Place the end of the stick into the notch on the piece of wood or bark. Rub the stick quickly between your hands so that it creates friction against the piece of wood or bark.
Drop the piece of wood or bark into your tinder nest once the flame has formed. Do this carefully so that the flame does not go out.