The simplest way to trade commodities is to buy and sell them straight from a commodity broker. This is not necessarily the best way to trade commodities, however. Going with commodity futures holds much more potential. And if you do it right, you will never be held responsible for the storage or transportation of the commodities you trade. The buying and selling of commodity futures is a very busy marketplace, and for the vast majority of traders, this situation never materializes because they can find a buyer for their contract long before it reaches its expiration date.
Commodity futures do come with a degree of risk, however. By being locked into a certain obligatory date, they do not have the same flexibility that comes with options or Forex Arbitrage. Still, a commodity like oil or coffee has a very high liquidity and you can easily find a buyer for your contract, regardless of what the terms are.
Commodities began as a way for farmers to protect themselves from fluctuations in crop prices, but have emerged over the centuries as a way for astute traders to make a profit. By trading commodities you do have a bit of risk, but this is true with any type of trading. Minimizing that risk is a bit harder with futures, but thanks to a liquid market and computerized brokerages, you can always find a place to trade your commodities within moments of deciding that you want to. Commodity trading needs to be approached with caution, but the markets have made it so that this risk factor is minimal.