Many Short Deck rooms use modified hand rankings: flush beats full house (because flushes are harder / houses more common depending on ruleset). Confirm the posted rankings before you sit.
Also common: A-6-7-8-9 can play as a wheel-type straight in some rule sets. Know the room's straight rules.
'Check the ranking rules' (short deck, G0): Confirm rankings and antes every room; don't import full-deck set worship.