The following is the text from an unschooling presentation I gave on the internet June 1998. But I can tell you what works for us, and what I've seen work for other unschoolers. The central philosophy is child-directed learning.
Children determine what they learn, when they learn, how they learn, and why they learn.
Grades, grade levels, semesters, testing, and imposed lessons simply don't enter into our experiences. We offer, we might even try to persuade, but we never force, threaten, or set up reward systems for doing academic work. We read a lot, play on the computer, visit the library, observe nature, and pursue whatever our current interests are. We believe that children have a natural love of learning. We believe that, given a rich environment and involved parents, children will exceed any expectations we might have had.