You can purchase a single asset class such as the United States Oil Fund (USO) or a diversified basket such as the iPath Dow Jones UBS Commodity Total Return ETN (DJP). Examining factors such as risk tolerance, investment goals, tax implications and qualitative drivers of price action should be primary concerns when considering an allocation to the commodity sector. On the flip side, if your investment criteria demands long-term growth with concerns about fighting global inflation, then commodities may make sense in the context of a well-diversified and balance strategy.