here's what helped me:
to go upwind, forget about going upwind.
(don't concentrate too much on it)
best is to ride out, jibe and seek youself a point only slightly upwind of your position.
look at this point (if your head points, your body'll follow, like fokiten said).
stiffen your body, lean back, park the kite at about 45Ã‚Â° and ride there.
it's important not to do any wipe outs
if possible, try the material of another rider
about your weight, when he's able to go upwind with it - so you can see, if something in your setup is wrong.