Two tips that have kept me in good stead throughout my travels that I’d like to share with you are these:
Eat where the locals are eating.
Look for food that you can see being cooked.
Regarding the first tip, the logic is simple. Generally speaking, food establishments stay in business not because of the tourist trade, but because of the locals that eat there day in and day out. If you come across a place that is busy and full of locals, chances are it’s good. If it was making people sick, it would be neither busy nor full of locals.
In relation to the second tip, most of the street carts and hole in the wall restaurants in Vietnam have the raw ingredients and cooking stations in clear view. If something is being cooked fresh in front of your eyes, you can see for yourself exactly what’s going on. Contrast this to a restaurant with a closed kitchen that you can’t see.