The best way to learn this is from your instructor. I can give you the name of several techniques, but teaching you how to do them right you need an instructor present. Also there is more than one shoulder throw in judo.
Ura-Nage, or a body lock takedown, wouldn't be bad. You could also push out on the legs and take their back. Keep in mind that if you're someone who doesn't do Judo and you try to do these to a Judoka, you'll probably fail.
A leg reap by circling around and to the front of his leg. Kicking the back of the sweeping leg by dropping your elbow in on the captured arm and turning your hips in. There are over a dozen others.
Shoulder throw. Fast.
Say someone tries to do a shoulder throw on you ("seoi nage“ in judo), and they have turned their back slightly toward you trying to throw you, but you were able to slip out and step slightly in front of him with one of your foot, what would be a good counter-attack at this point?
