Often we hear people say, "they" know the numbers because a stock or the market moved a certain way the day before the event. It's mostly not the case. Even if that is indeed the case, there is no way to play it. When a stock goes up before the earning, it could be one of two things if we want to attribute the move to be due to the people in the know: they run up the price to dump it because the numbers are bad, or they buy with both hands because they know the numbers are good. It's moot.
APKT was up 6% during the day, only to tank over 10% after hours.
INFN, on the other hand, was up 5% during the day and popped another 10% after hours.
GMCR was flat during the day, and jumped 24% after hours.
How about SFLY? It rallied 6.5% during the day, only to dive 14% after hours, and finished the next session up 7.8% (that's over 25% move from the after hours low!!!) Who'd have thunk it?!
Earnings plays are casino plays however you slice it.