Buying or selling commodity contracts requires deposit and maintenance of margin money, a small percentage of the value of the contract on deposit with the brokerage firm as a performance bond. Initial margin is the amount that must be deposited when a position is first established. Maintenance margin is the amount that must remain in a trader's account during the time he retains that contract. See current margin requirements for selected contracts. Follow this link to TFC Commodity Charts' very useful Glossary of Commodity Market Terms .
Many new traders spend several months following a few markets on paper - called Paper Trading.
This helps traders explore several trading strategies to find what works best for their needs, plus helps acquaint them with charting techniques and technical studies. Here's a webpage that lists a number of paper-trading resources , or your broker can help you gather the needed information yourself for free from online sources such as the various exchanges and sites offering quotes, charts and even some market analysis.