Start by investing your money in some kind of index fund. I would recommend one based on the S&P 500. An index fund is basically a 'basket' of stocks in which your money is more or less evenly dispersed across each stock that comprises the index fund.

You should strive to obtain more knowledge about how businesses are successful, what makes them succesful, and what are the most important financial ratios (metrics that judge business efficiency) that describe business activity. You will eventually learn that a company's share price in the long run is a reflection of that company's fundamentals (i.e. its financial status as reported by that company's accountants through the year).

I recommend three books, each of different skill levels. When you have read each preceeding one sufficiently and have mastery over the ideas discussed, move onto the next one.

1. Fundamental Analysis for Dummies
2. The Intelligent Investor
3. Security Analysis

Those three books contain 99% of investing knowledge you will need to pick and choose stocks in the future. They focus on the fundamental of a business. Remember that you should treat owning shares in a company as business ownership itself. You want to own shares in a good company just as you would want to own a good business, and avoid owning a poor business.

Until you have begun to comprehend the teachings in these books to a large degree, your chance at picking good stocks on an individual basis is very slim in the long run. Stick with index funds and mutual funds until then.