All of the above is correct. What flying monkey is talking about, is that if your motor is turning "the wrong way" the impulse when the engine accelerates and the propeller wants to stay moving the same speed can cause it to loosen up the nut holding the prop on. I've lost a prop or two like this. A nylock nut alleviates the issue. They also sell electric motors with reverse threads to keep this from happening. The most important part as hondo points out is to make sure the letters and numbers are aimed the direction of flight.