If you own a stock, you own the company. How your stock performs is dictated by how the company performs. You need to be aware of the challenges and opportunities facing the business and you also need to know where the business and its products are in their respective lifecycles. This is often a qualitative assessment but if you wish you can also choose to quantify various aspects to help you further fine tune your stock selection. In my experience, quantification is not necessary. Being precise is not the same as being correct.