I'm told that the technical term for how Riker sits down is "Sitfucking."
Him putting his leg on Data's console and hunching is so he can stay in frame. He is pretty tall, after all.
As for the whole foot on Data's console posture, Riker did it most often but both Picard and Data were seen doing it as well. In either case, it earned Riker the nickname "Stinknuts" here on this very BBS a few years ago. I made this thread bomb back then.