Low stress training. Gently bending the stems, securing them to a stick, that kind of thing. The goal being to get more light everywhere. So on yours, some sticks around the outside, and some cut-up panty hose or gardening ties to pull the limbs gently away from the center.
Super-cropping - I would watch a video - but that is actually bending the stems in a specific way so they are a complete 90 degree angle. It stunts the growth for a bit from what I understand, but then it goes crazy.
Read! Watch! Great resources here and on YouTube. There is a particularly good one by Chef D