Wedding gift etiquette is less rigid than it used to be. The old rules ("cover the cost of your plate", "give cash in odd-numbered hundreds for luck") have loosened into a broader convention: give what you can afford, give in a form the couple will actually use, and give on time. Relationship and geography are the two variables that matter most.
This guide covers the standard amounts by relationship, the shift toward cash over registry objects, the timing (before or after the wedding), and the special-case rules for destination weddings and group gifts.