By using a stock screening tool an investor is able to follow a strict set of criteria that he or she requires prior to investing in a company. For example, an investor could screen stocks by entering the following criteria: "listed on the NYSE", "in the telecommunications industry", "has a P/E ratio between 15-25", and "has an annual EPS growth of at least 15% for the past three years". The screener would then produce a list of stocks that displayed all of these attributes. In this example stocks are screened by using only four criteria; however, you can screen stocks by as many criteria as the particular screener you are using will allow.

Stock screening has replaced many days' worth of research with a few mouse clicks.

Most good stock screens have similar characteristics. Like anything else you find on the Internet, some are easier to use than others are. In addition to being easy to use, the screen should have a robust database of information on each company. At least five years history is the minimum for research purposes.

The screen should contain both absolute and relative information. That is, in addition to sales figures, the screen should show you what has the increase (or decrease) been year-to-year. Percent changes are often more telling than absolute numbers.

Stock screeneing is just a tool; however, they should be the first tool you master as you begin learning to do research.