The best strategy, it seems, is to buy bitcoins and then unplug the internet for 6 months and wait 
6 months is much too short a time. 24 months is a better minimum hold time for a big fat greasy profit.
As some bears have been quick to point out, there have actually been 6-month periods (e.g. late 2011) when the price fell.
5 years is probably a better minimum hoarding time. By then the s-curve will have probably been through the vertical phase, no longer parabolic, and leveling off.