Almost everyone knows someone that has done really well in the stock market, and they often also know of somebody who has lost a great deal of money the same way. You need to be able to tell what are good investments and those that end up losing you money. You can better your odds by becoming knowledgeable about investing and minimizing transaction costs by taking a more passive strategy.
Make sure that you have realistic goals when you start investing. For the most part, instant wealth is not a realistic goal. There are a few stories of people who made killings overnight, but thinking that will happen to you will very likely lead you to take undue risks. When you keep your risk reasonable, you will increase your chance for success.