When Jim Cramer says "buy," the stock price moves. No one person has individual investors more abuzz than Cramer. His television show, "Mad Money" appears on CNBC every weekday at 6 p.m. and 9 p.m., and it's hot.

Jim Cramer is very smart, and he works very hard. Ever since he created his web site, he has been interested in bringing Wall Street to individual investors. His latest show is a big success, and it highlights his in-depth knowledge of the equity markets.

During the show, he is continually offering his "buy," "sell," and "hold" advice on individual stocks, and usually offers an in-depth stock analysis for viewers every week. One of the stocks he recently talked about was Distributed Energy Systems Corp. (NASDAQ/DESC).

After Cramer said DESC was a "buy," the stock moved up one full point the next trading day to approximately $10 per share.

DESC is one interesting company. We first brought this company to your attention back in July as an attractive alternative energy play. Since then, the stock has just about doubled.

This innovative company is actually a combination of two companies, one that is developing technology for hydrogen production and fuel cells, while the other is an installer of more traditional energy systems in office buildings, hotels, and hospitals. The combination couldn't be better. You've got a real business that's profitable, in addition to a development company working on next generation energy applications.

The stock is now all the rage on Wall Street, and Jim Cramer's attention certainly illustrates the power of the media. Of course, the best trade is to buy before these kinds of stocks become Wall Street darlings. The best way to discover this kind of stock market opportunity is to focus your attention on investor psychology. With oil and gas prices rising dramatically all year, the alternative energy investment theme makes sense.

Once you determine an investment theme with staying power, it is actually quite easy to look up all the stocks within a market sector, and choose from those offering the best prospects.

In the equity markets, everything is relative. Speculating on investor psychology is as important as the actual stocks you pick.