So you still want to know how to do the pinch test?

It's fairly simple. If you pinch the fuel off and the engine speeds up just before it runs out of fuel, the engine was too rich. If you do the pinch test to an idling engine, then the lowspeed needle is too rich. You can do the test with the throttle wide opened and it'll tell you how the highspeed is set. But thats easier to do with "experience" (what you just picked up in the post above). If you pinch off at idle and the engine just stops, the lowspeed is probably too lean. Simple?

When an airplane engine dies on throttle up, it's usually one of two things. Weak plug or bad lowspeed needle setting. It's usually the lowspeed or idle needle setting. And it usually happens with new engines that're just then breaking in.