Wear safty goggles, or face shield, and keep dangling or loose objescts away from the machine.
Make sure that the bench grinder is properly secured to a surface.
If it is not properly secured, then the grinder could vibrate and move while in use, or even fall to the floor.
Check to see that the gap between the face of the grinding wheel and tool rest (aka work rest) does not exceed more an one-eighth of an inch.
Minimizing the gap prevents your work from getting wedged between the spinning wheel and work rest.
Make sure the metal you are using is ferrous (steel only). Do not grind aluminum, copper, bronze or brass.
Flip the switch in the middle of the machine to the on (left) position.
wait for it to come to full speed before touching material to it.
Make sure the piece of meatal is secure (ie. holding it in a vice grip).
Begin grinding the meatal until you are finished.
Switch the machine to the off (right) position.