Maybe letting your legs bend a bit, hold your lumbar, chest and pecs, as well as the hips maybe. You just have to experiment with these sort of things, they'll come to you in no time.
you'd kick as if you were on the ground, but you know, in the air.
can you be a bit more specific, what are you trying to do? I sort of twist kick, or a straight up jump kick, with the regular jump kick just up and swing your leg at your enemy in a sort of roundhouse or front kick manner.