First of all, you need to change spark plugs annually or every 60,000 miles. Also, required tools include a spark plug socket, feeler gauge, and torque wrench. Replace plugs individually, inspecting for defects and correcting electrode gaps. Adjust incorrect gaps with the feeler gauge. To remove a plug, disconnect the wire and boot, and clean with compressed air. Examine old plugs to evaluate engine condition. If any electrode is damaged or the gap is too large, replace all plugs. Install new plugs using rubber tubing to avoid cross-threading, tighten to the specified torque, and connect the plug wire. Repeat for all plugs.