If you want to learn, most brokerage companies have a great deal of information on the how's and the why's of investing. A company like Etrade.com (no affiliation) is quite literally information overload. It is a good place to start reading and understanding.

As far as learning to tell a good stock from a bad one, even the experts don't get this right all the time. Which is why I will agree with brandtb on buying an index fund or etf for spreading out the risk associated with just buying one or two stocks.