How can you tell when a machine is due to hit?

A word that should not be in any slot player's vocabulary is "due." No machine is ever "due." The RNG constantly cycles and conceivably could pay out two top awards in the space of two pulls, and then not pay another for years.

The only way to even get an idea about individual machines is to "scout" them over an extended period of time. Keep mental (or even written) notes about which machines you and other players seem to win on again and again. Those machines that pay out consistently will be the ones on which to concentrate your play. No, it's not an exact science, but even a little information can go a long way.