It is simple, they buy Altcoins on its DUMP state, then sell it on its PUMP state, just like that, for them to easily know when is the right time to sell their Altcoins and they are going to wait when someone's is going to DUMP his Altcoins and they are going to buy it, and sell it again in the right time. This process is just keep on repeating all the time, that is what the Traders do, though we have our own ways on Trading, this one is the most used strategy that I am seeing that is why I suggest it because it is really effective for us not to lose any profit.