Love the reply Eristic!
Rosebud I have a couple of box in medium sized pots that I got when about the same height as yours. I've gradually shaped mine into round ball type thingies. Definitely not perfect but still not a bad attempt. I have read before about using chicken wire to help create the shape you want, but I've never tried it. I tend to give them a re-shape and trim when the new leaves are fully out and use a large pair of shears and SLOWLY and GENTLY clip away, and keep turning the pot around. All a bit hit and miss tho.
It will also depend on how ambitious you are in terms of what shape you want and I think at 12" high you will have to wait a couple of years before you start snipping in anger :D