Some of the ways I have learned is through losses, like most. Failure is often a huge lesson. I tend to think about what's going on on the world, and how that can impact various stocks. But that alone, won't always work. Its important to know what you hold. Follow the stocks, and keep up to date on what they're doing. I'm still a work in progress, but learning to read charts is vital. Where has it been, where is it going? What's the projected price? What do more experienced investors say? I guess, like anything else, question everything and then question some more.