k...i've got a quick and easy one that patrick coté showed at a seminar
when your opponent has you in the clinch with his hands cupped behind your head, quickly bend your legs like you're going down for a squat then cup your hands on his elbows closer to the triceps then the forearms
explode up hard and fast holding onto the elbows, this will cause your opponents arms to straighten much like an armbar and he will be forced to break the clinch
if your opponent is in closer and is stronger, you may just end up lifting him up by the elbows, that's ok since you still have the advantage: his feet are off the ground and you can go for a throw/slam/trip/etc.
it'd quick and the easiest/most effective technique i've learned so far to break a clinch...it needs to be executed fast or the opponent will know what you are doing or you'll grab a knee with your face
The surest way to corrupt a youth is to instruct him to hold in higher esteem those who think alike than those who think differently.