When changing spark plugs its important to verify that you have everything needed for the job. You will need a new set of spark plugs appropriate for your vehicle, a gap gauge, dielectric grease, and a spark plug wrench or socket and ratchet of the proper size for your plugs. You may also need a screwdriver or socket to remove engine covers or coils and penetrating oil if the spark plugs are seized. Some cars have spark plugs that are very difficult to replace so before starting locate the spark plugs and verify that you will be able to complete the job.
Before installing the new plugs, verify that they are gapped correctly using the gap gauge. The proper gap is normally somewhere between 0.035” and 0.060” and should be listed in the owner's manual as well as on a placard under the hood. If the gap is not correct carefully bend the ground strap without touching the electrode.
Spark plugs should be changed when the motor is cold, as the plugs will be easier to remove and there will be less chance of damaging the threads. If necessary remove the engine cover to allow access. Each spark plug should have a wire or coil attached to it which will need to be disconnected before the plug can be pulled. Work on one spark plug at a time to ensure that the wires do not get reconnected incorrectly. You may need to remove a retaining nut before slightly twisting and pulling the boot of the wire or coil from the plug. Ensure that the spark plug well is clean using compressed air or a vacuum so there is no chance of debris getting into the motor. Using the spark plug wrench or socket remove the old plug; if it's being stubborn spray some penetrating oil into the spark plug well and allow it to soak for a few minutes.