Stocks are one area of investment that you really want to do your homework. In the US, the SEC requires that the financial information for a publicly traded company must be clear and as reliable as possible. Learn to read financials, learn how to do the ratios and follow the history in a company. If your just getting into stock investment, stick with solid companies that are well known and well managed. Once you build a portfolio, then play with the penny stocks.
All the big investment hubs, CNNMoney, Wall Street Journal, even Fool.com are great places to do your research. Your broker probably also has tools available to help weed out the good from the bad.