Before using a fire extinguisher, always read the instructions on the label. There are different kinds of extinguishers for different fires—if used incorrectly, they can cause the fire to spread, re-ignite, or even explode. Once you have sounded the fire alarm and confirmed a safe escape route, you may use a fire extinguisher from a safe distance to dowse the fire.
A good way to remember how to use a fire extinguisher is the acronym PASS:
Pull the pin in the handle
Aim the nozzle at the base of the fire
Squeeze the lever slowly
Sweep from side to side at the base of the fire