For this contest, sniping doesn't work, so just be nice and guess in the middle of other people's guesses.
I think it's just a matter of pure luck, with more chances for those which predict a price closer to the deadline (August 30th). To be more precise, in case of those which took a chance earlier, when the contest launched on August 17th, there are more chances for BTC to go toward a different price than the predicted one, compared to the case of those which estimated a price on August 30th. The latter ones have more chances to win than the former ones. Of course, the contest is also about pure luck and everyone has a chance, but I believe that the winner will be elected from those which predicted later a price (meaning after August 28th).