The tinder bundle is the most essential element in making fire. It is used to blow the coal / ember from the fire set into an actual flame. Fluffy and fibrous materials are key. You want to fuzz up the material so it will ignite easily. You want it to be soft and pliable. To achieve this, vigorously work the tinder between your hands rolling it round and round. Move up and down the full length of your tinder until it is the consistency of cotton batten.
While working the tinder, save all fine bits and dust falling down from your hands. This finer material should be put in the nest last and will mark the place where the coal / ember will be placed. Make your tinder bundle by tying your material in an overhand knot and then tucking the ends towards the center to form a nest shape. The bundle should be at least the size of a fist. Stuff additional tinder into this knot until the nest is dense. This will keep the coal / ember from falling through the bottom.