I achieved this two ways. One involved being home and just gently tossing them down, but in a manner to let them know that it's not ok. The second is a little more effective. It's called hsss cat or something like that. It's a motion sensor attached to a bottle of compressed air. My cats don't jump, but my girlfriends do, and this is a savior. When the cat jumps up and triggers the unit, a burst of compressed air ("hsssss") goes off in their direction, not harming them but scaring the CRAP out of them.

Also try a squirt bottle of water. My cats responded to that and if they even see it, they know not to be bad!