One of the biggest mistakes day traders make is simply trading too much, said Phil Flynn, a senior market analyst at Alaron Trading in Chicago.

"You have a tendency to kill yourself because you're going back and forth several times," said Flynn, noting that each trade comes not only with a risk of betting the wrong way but also a commission fee. For the contracts traded, most of the Web sites will charge about $7 a trade. (To find some of the sites search for "commodities trading" on the Web).

Flynn suggested setting a limit on not only the dollar amount you're willing to lose, but on the number of trades you're willing to make in a day.

He said the limit will be different for everybody and can even be flexible depending on market conditions, but generally thought something more along the lines of 1 to 5 was better than, say, 20 or 70.