I'd just add my own (uneducated) experience to Wahine's excellent advice. My heel pain is a little higher up - the kind that masquerades as Achilles tendinitis rather than plantar fasciitis. Mine is all about trigger points in the calves. No amount of stretching or good form will make them go away. I have to work on them directly, and it's tough because they're SO deep and ingrained. But I hold out hope that one day I'll have them all worked out...