Food
Fresh
Vietnam enjoys a large agricultural sector and a long coastline that produces excellent seafood. Farm-to-table and boat-to-table are the norm rather than the exception. In rural areas, I did not get the feeling that there is as much refrigeration as we see in the U.S., resulting in what is served being very fresh.
Social
Meals are social occasions and the servings and sides are often family-style.
Inexpensive
Meals in rural and non-tourist areas are inexpensive. We seldom spent more than $5 U.S. per person for an excellent, multi-course meal with beers.
Safe
Go where the locals go. Eat on meal schedule times when food is fresh. Watch the preparation and clean-up (both visible in most places). Be smart.
The street food scene is amazing and you must try it. You get to see all of the operation.
Food establishments specialize in one or two dishes. For variety, you shop by choosing the restaurant rather than from the menu.
Meals are early and generally follow set times. Show up late and the restaurant may have stopped serving. Or risk getting what did not sell.
Most street food vendors are owners with their reputation and livelihood at stake. It shows.