well ive heared alot of ways to stop and why not to use em...

ive heared stoping the flyweel is fine unless you having a runaway, but if its at idle it should be fine

i think taking the air filter off and covering it would be best to do in a runaway, getting a little dirt in the carb that you can clean out is better than having an engine run at high rpms, not moving for a long time.

pinching the fuel line will work if its at idle but if its high rpm then the car will run really lean and could cause serious engine damage

when you cover the exhaust it puts alot of backpressure into the fuel tank causing a lot of fuel going through the lines in the the engine, then when there is alot of fuel the engine cant combust and cant compress the fuel so it could car a connecting rod to bend or somthing else similair.

hope that helped...