The best way is to not let it get to the overheating point, but...
If the engine overheats, it will run like a champ up until it stalls. The stall will be caused by the excessive heat vaporizing the fuel at the inlet to the carb (this is bad). The engine will then refuse to start until it cools down. This is caused by two things. The heat still vaporizing the fuel and causing backpressure down the fuel feed line, AND the engine being too damn hot to properly ignite (kind of like the timing in your real car being off).
The best method for checking this is to get a temp gun (I can't believe I am suggesting this...but believe it or not I just bought one for the first time in nearly ten years of doing this hobby).
The reason I suggest getting a temp gun and not allowing the engine to reach the overheat point is that too many overheats reduce the life of the engine.