How do you replace the spark plugs on a Mazda 6 4-cylinder?

To replace the spark plugs on a Mazda 6 4-cylinder, first, ensure the engine is off and cool. Remove the engine cover if applicable, then locate the spark plug wires or coils and disconnect them. Use a socket wrench with a spark plug socket to carefully remove the old spark plugs, checking for any debris. Install the new spark plugs by hand to avoid cross-threading, then tighten them to the manufacturer's torque specifications before reattaching the wires or coils.