I always click in the little pond on the west side of the island. Bad advice because despite the fact that I always used to win from there, I never do now.
I think it would be random. Think about it, if it wasn't random somebody would be cleaning it out every time it got a decent amount of NP in it.
I used to use the drift theory, but lately, for me at least it hasn't been working too well. I'd guess that there aren't any cheats and that the spot is random for jackpot and such.