Remove the spark plug on your hedge trimmer by using a spark plug wrench and turning it counterclockwise. Replace the spark plug with a new one of the same type. Screw the plug in by turning it clockwise until snug.
Check the air filter on the machine's engine. It is usually located on the side of the engine. Remove the air filter cover by unscrewing the butterfly nut or the screw holding the cover on. Remove the air filter and examine it. Hold it up to the light. If no light is visible through the filter discard it and purchase a new one. If light is visible, clean the filter with gasoline. Dry it off with a rag and put it back. Reattach the cover.
Remove the fuel filter. Do this by using needle-nose pliers to pull the filter out of the tank. Use the pliers to pull the filter off the gas line. Replace the filter with a new one, and push the filter and gas line back into the gas tank.
Replace the carburetor if your hedge trimmer continues to run poorly. This is an involved task which requires experience as well as access to the correct parts. This job is best performed by a skilled small-engine mechanic.
Apply a lubricant, such as oil, to the hedge trimmer blades. If the blades are double-sided, apply oil to the bottom side as well. Wipe excess oil away with a rag.