Learn "Technical Analysis". Basically, it's the art and science of understanding patterns, riding momentum in price movements and mastering market psychology.
I wouldn't encourage scalping /day trading though. It's a waste of time, unless you really get good at it. Better research more about the assets you're looking into investing. This is what they call Fundamental Analysis. If you understand what exactly you are buying and you think it is undervalued, then you'll be good.