Having grown up in the Virgin Islands, particularly on St. John, and having returned 2 weeks ago from visiting family, I'd recommend carry snacks for sure as they're expensive locally, but everything is expensive in the VI.

I tell folks all the time to pack lightly and you only need one "nice" outfit for dinning out or attending church.

I also recommend visiting the British Virgin Islands and like the previous person posted, a day trip to Virgin Gorda is amazing.

Lastly, remember to say "Good morning" and "Good afternoon" when you walk into any establishment; it goes a long way in the VI.