The following steps should get you started. Verify the firing order (1-8-4-3-6-5-7-2). Check for active arcing between the spark plug wires and the exhaust manifolds (this is accomplished most easily in a dark location or at nighttime). Make sure there are no cracked spark plugs. Using a good flashlight, look deep into all of the spark plug wire boots at both ends of the wires. Look for any greenish discoloration of the terminals or black soot accumulation. Check the length of the wires for any gray-white ashy deposits, hard spots, or other indications of heat distress of the wire insulation. How do the business ends of the spark plugs appear? Are the electrodes rounded and burned back or sharp and clean? Do the insulators appear fouled with carbon, oil, ash? Are chunks of the insulators missing from around the center electrodes? Post clear pics if you are unsure. How many miles ago was the last tune-up performed? Inspect the cap and rotor for terminal wear, housing cracks, and/or carbon tracks.