Quote from Echieo:
I often hear traders on this site saying they have simple streamlined systems that they backtest. How do people select securities to trade with these systems. There is a lot of talk about signals but not much on picking securites. How does one test a system even if its as simple as a moving average crossover? Do you pick an arbitraty day to start and run it over all stocks that meet your criteria? How does one apply this when there are so many stocks out there to trade?
That's a very good question. And one reason why many traders gravitate toward index futures.
But if you are determined to trade equities, one way to answer the question is - what makes sense in terms of your strategy?
As a simple example, if you are into buying pullbacks in can make some sense to follow a list of fundamentally strong stocks with growth. Because they'll often tend to attract buying interest on weakness. (Assuming there is any buying interest, which is lacking across the board right now.)
Conversely, if you are shorting, it may pay to look into fundamentally weak stocks that are showing some strength.
Use a scanning site (Yahoo has a good one) to build a list of stocks that you think might make sense with your strategy. Backtest that against a control group. You may find that the results do have some logic that can help you.
Also look at volatility, volume, etc. to find what works best with your system.
Bottom line is, good systems generally have some underlying logic, as does selection of the instruments to trade those systems.
Finding a good combination of strategy and instrument isn't easy, and its why success doesn't happen overnight.