Better international relationships. A substantial amount of the world's oil-supplies can be found in the Middle East and as long as the conflicts there haven't been solved, oil prices will likely remain high. For starters, a solution to the conflict between Israel and the Palestinians would probably be helpful. I guess peace in the entire region would have a very positive effect on oil-prices.
This, however, is kind of a political thread and I'm not going into who's right and who's wrong here.