Position
Where you sit relative to the button — which decides when you act on every street.
Acting last is the closest thing poker has to a structural cheat code. Every street, you watch what everyone else does before committing a chip: checks tell you something, bets tell you something, and you get to use all of it. The seats have names — the blinds, under the gun (first to act), middle positions, the cutoff, and the button, who acts last on every postflop street — but the names matter less than the single fact of who acts after whom.
The earnings data is blunt: across big player pools, the button is the most profitable seat by a wide margin and the blinds the least. The same player with the same cards makes dramatically different money depending on where they sit, because information compounds — every street you act last, your decision is better informed than everyone else's.
The practical rule is range by position. Under the gun at a nine-handed table, eight players act after you, so enter with hands that don't mind company: big pairs, big aces, roughly the top 10%. On the button, with only two players left to wake up with something, the correct raising range balloons to a third of hands or more. Playing the same range from every seat is the single most common structural leak in low-stakes live poker.
Home games add a wrinkle: in self-dealt games the button deals, and everyone needs to trust the rotation is honest. Keep the dealer button moving exactly one seat per hand, every hand, and let position do its quiet work. Your session log won't record where you sat, but your results will. The hands you add in late position — suited connectors, weak aces — are profitable there and bonfires early.