It's very hard to say why and how they do it because if we knew, we would already have been one of them and wouldn't want to spill the secret but yeah, trading requires a LOT of patience along with good market, political, economical, geographical knowledge as well as psychology of consumers and government department incharges to be taken into account to make a very good prediction of any company before investing in them and make good profits. I guess that's why the number of successful traders are so low!