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Gasoline often carries a static electric charge. Place the can on the ground before filling it, where any static electric charge carried by the gasoline can disperse. If you fill the can on a plastic surface, sparks may occur and ignite the gasoline. Remove the cap of your gas can and open the vent located at the top. Place the cap on the ground next to the can. Pick up the pump and insert the nozzle into the can, making contact with the inside. Squeeze the pump to dispense gas into the can. Fill the container no more than 95% full. This will accommodate volume changes that might occur in different temperatures. Once you are done filling the can, remove the nozzle. Put the cap back on and seal it as tightly as possible. The gas can should be completely closed.

Summary:
Place the can on the ground next to a gas pump station. Place the gas pump nozzle into the top of the can. Fill the can up to 95% full to prevent spills. Seal the can tightly and close the venting hole at the top.