An R/C model engine can be a very dangerous item if not handled with care and respect. Accidents can and often do happen. Here are some safety tips that are well worth remembering.
Regularly check the tightness of the prop nut, especially on wooden props. Routinely inspect the tightness of the engine mount and firewall by grasping the nose of the plane with one hand and the engine spinner with the other and firmly pulling the engine up and down and side to side.
If your propeller is chipped or cracked, replace it. It could be a danger to you and those around you.
Plastic propellers have a razor sharp edges that must be sanded before use.
Avoid wearing loose fitting clothes or jewelry.
Keep spectators well away and especially away from the direction of the rotating propeller.
When starting your engine manually it is wise to use a chicken stick.
Ensure that the throttle is closed or very nearly closed before starting your engine. Starting at any speed higher than a high idle increases the risk of serious injury.
Be sure your radio is on and functioning before starting the engine. It's a good idea to open and close the throttle with the radio to insure the throttle is functioning properly.
Make sure that your starter and glow plug battery wires are well away from the prop.
Ensure the model is secured so it will not move when the engine fires. Don't release the model until you and others are out of harms way.
Never reach over a rotating propeller. Make slow, deliberate moves when working around a running engine. For added safety, picture the propeller arc as being much large than it actually is.
Never throw anything into the prop to stop the engine. You should be able to stop the engine from the radio, but if it does not stop, pinch the fuel tube to cut the fuel supply. Adjust the radio so that you can stop the engine from the radio in the future.
Develop a safe routine for starting your engine. Be consistent in where you orient yourself, flightbox, radio and wires relative to the plane. By making this a habit it can help you avoid awkward and unsafe situations.
SAFETY IS NO ACCIDENT!