I keep track of what returns I’ve had off what slots every session, along with my dad who does the same.
I stay away from the ones with massive jackpots, and go for multiple-feature slots where you can often get good return off a single feature spin rather than hanging on waiting for landing a bonus for free spins.
I’m sure that’s true really, after all that’s how the bookies win most of the time…but I’ve tried quite a lot of slots, and although it may well be all dumb luck, I can get a feel for how productive a slot is across average play sessions.
