My personal opinion is that the average person should stay away from day trading, as I believe it is essentially a form of gambling. Here is a brief excerpt from the Day Trading wiki page defining day trading, and a link to the full post is at the bottom.
Day trading refers to the practice of buying and selling financial instruments within the same trading day such that all positions are usually closed before the market close for the trading day. Traders that participate in day trading are called active traders or day traders.
Some of the more commonly day-traded financial instruments are stocks, stock options, currencies, and a host of futures contracts such as equity index futures, interest rate futures, and commodity futures.
Day trading used to be the preserve of financial firms and professional investors and speculators. Many day traders are bank or investment firm employees working as specialists in equity investment and fund management. However, with the advent of electronic trading and margin trading, day trading has become increasingly popular among casual, at home traders.