La [version française est ici][french].
Here I write quickly about the basics you should be aware of.
Viet Nam is a developing country, so there are a lot of things that will look sketchy to you when dealing with getting there, and once you get there.
Also, if you've never been in a developing country before, you might want to read a bit about Viet Nam before getting there. There are many things you take for granted as normal behaviour that aren't necessarily something you should do there. For instance: