How do you increase the height of a 14 year old boy?

Exercises are unlikely to affect your height very much at all, if anything all you would really be able to do would improve "core" or postural strength, which would make you hold your posture better and possibly make you seem taller. Otherwise I'm pretty sure that your height is determined genetically and altered very slightly by the environment (i.e. like having a cold stunts your growth for it's duration)