Rules for living in the one piece world:
Never eat strange fruits.
Mind your table manners, or your ass is toast.
Pirates rule all. Marines, lawyers, ninjas, and especially megalomaniacal men with super-natural powers bent on taking over countries and, by extension, the world.
Drug abuse should only be done for 3 minutes at a time.
Beware of swordsmen who mop your floors.
The interest on all loans is 200%. Or 1000% for royalty.
One's manliness is determined by the length of your nose!
But most importantly, everything should be fun. Everything. From meals to fishing to sailing.
Because if you ever do anything to upset someone, you will have violated the most dangerious rule of all...
You don't mess with Luffy.