The trick you see is to buy when the price is low and the sell when it's high.
Well, I follow the contrarian school and buy high, sell low (relative of course to previous holdings). That way I'm holding when it grows, and removing positions as it falls. It has the additional advantage of bucking conventional movements by most speculators. I have made some 1-on-1 individual transactions outside of the exchanges as well as through loans (1-on-1 short contracts), and done quite well.