All lights flicker, intermittently.

Most likely an electrical connection but which one? Start at the battery make sure the connections are clean tight and secure. then look at the light switch connections. and powers and grounds. With the engine running wiggle wiring harnesses and see which one causes the lights to flicker, when you have found the offending harness look at the electrical connectors and junctions for corroded or shorted out or wires that may be going open circuit. Autozone have some popular workshop manuals for free on line once you register (for free) on their website http://bit.ly/autozone_repair_info. and get an online repair manual subscription.

I had that problem once and found i had the alternator belt a lil too tight