RSVP promptly
The couple cannot finalise catering, seating, or transfers until they know who is coming. Respond within two weeks of receiving the invitation. If you are genuinely on the fence, say so and commit by a reasonable deadline the couple sets.
Respect the dress code
Destination-wedding dress codes are often more specific than local weddings: "breezy formal", "garden-party chic", "black tie on the beach". Follow them. If the invitation says "no white", do not wear white. If it says "cocktail", do not wear jeans.
Budget honestly
A destination wedding typically costs the guest $1,500–$4,500 per person all-in (flight, hotel, food, gift). If you cannot afford that, decline gracefully without making the couple feel bad. Do not accept and then cut corners that embarrass the couple.
Gifts are optional but appreciated
The old etiquette rule — that your travel covers the gift expectation — still broadly holds for destination weddings. A small meaningful gift ($50–$150) is thoughtful but not required. Cash is almost always welcome if you prefer it.
Do not bring a plus-one that is not invited
Read the invitation carefully. If it says "Mr. John Smith" (no plus-one), you are invited alone. Bringing an uninvited partner to a destination wedding is a particularly expensive mistake because the couple has paid for a specific head count.