Being incredibly physically fit is crucial. Lots of TONED muscles, (not just muscle mass) allows for some crazy feats. Aerobics and cardio exercise are important - not just lifting weights. Flexibility is important. Lots of stretching - yoga and other stretches are recommended. Hand/finger strength is a must. Spring or foam hand trainers are good (like really stiff stress balls). Check the instructables on the right 'related', or just search parkour and theres TONNES of info.