Great questions, Mike, and likely one of the most important for a software developer -- what factors really work? If you have a large database then you could test things yourself but you would need some knowledge of statistical methods (probably some form of regression) to know if the factor is a real predictor or just some random blip. Statistics is a fascinating topic but it's mostly over my head except in it's most basic forms.
In lieu of that you could use things that others have researched. A good place to start would be Dave Schwartz's Percentages and Probabilities. It's an updated version of Quirin's research from the 70s. I am working on my own software and using some of the things that I learned from P&P as a base. And it's currently on sale. (Dave, you can send me the commission check later.
) P&P is a few years old now but I doubt that the IVs and $Nets have changed substantially. My feeling is that the high IV factors have gotten even stronger but the $Nets have probably decreased somewhat.
And this thread might provide some good ideas to test, and I emphasize
test. Some ideas might seem logical and that they will work but won't hold up under scrutiny. And it's not likely that someone will give away their secret factors.
