I'd like to try this judo backtrip, but I haven't been able to set it up in sparring yet.
Get sameside collar grip and sameside cuff grip, straightarming their arm down, pulling them towards you and you going backwards a bit. You're wanting their other arm with a crossbody grip. Usually it seems like this starts with his arm going over your headside arm onto your shoulder/tricep. Once you have broken his posture down a little so that he's leaning forward, let go the sleeve, reach up under your headside arm, and strip his grip from your gi. Then straightarm THAT arm down, still holding/stiffarming his collar. You're moving him so that you can end up standing next to him, facing same direction as he is, with your OUTSIDE foot lined up next to his INSIDE foot, and you "steal the base" by sliding your inside foot along the mat in a straight line behind his heels so that your pelvis collides with his thigh. It's something of a sacrifice trip I think. You end up taking mount and still having his arm--setup for armbar is pretty easy.