Even though extinguishers come in a number of shapes and sizes, they all operate in a similar manner.  Here's an easy acronym for fire extinguisher use: "The PASS Method"

P A S S - - Pull, Aim, Squeeze and Sweep

There are four different types of Fire Extinguisher's for all the different Classes of fire! And here they are: Dry Chemical, Halon, Water and Carbon Dioxide