What are the two quickest ways...

...to make the cost of anything go down?

Increase supply or reduce demand...

DO NOT INCREASE TAXES

Build a refinery or three, tap into our domestic oil deposits, build nuclear power facilities, invest in affordable electric cars that people actually want to drive(Tesla Motors?)

I'm not saying ignore Solar, Wind, or Hydro power, but Nuclear provides the biggest bang for the buck (pardon the pun). It is as safe as anything else we have, it is efficient, and is more eco-friendly than Coal, Natural Gas, Oil, etc.

Bio-fuel is great too, however you must still blend bio-fuel with petroleum fuel for automobiles to function correctly. Diversifying to automobiles that are electric eliminates petroleum fuel all together. Making cars that people will actually drive redirects the demand for petroleum based cars entirely.

Sure there will still, and I imagine always, be a need for petroleum based automobiles - especially in the commercial sector to move goods from point A to point B - but applying electric cars where it makes sense (large metropolitan cities) and combining them with personal solar power cells would virtually eliminate the cost of personal transportation - especially in the Southwest.