How does OPEC determine the prices of world oil?

Oil price is not directly decided by OPEC. Price of any commodity is decided by demand and supply equilibrium. Besides, in the case of oil, political factor plays a major role. Also valuation or devaluation of Dollar does affect oil price.

OPEC has only one factor in its control and that is 'production'. If production is increased so as supply is more than demand, prices are likely to fall. Vice versa is also true.

But other factors also play important role.