Do not be annoyed or angry
Of course, on your visit to Vietnam, you will be surrounded by many different people from all walks of life. Therefore, it is strongly advised that you should not give an arrogant, annoyed or angry look to the locals while you get a chance to roam around their roads, parks, historical places or restaurants. In cases like these, foreigners are often approached by people who have a heart for English speaking persons or they want to learn the language, therefore you should remain kind with them at all times.
Keep your documents with you at all times
It is important that every foreigner should keep his or her documents with themselves at all times whenever they are in another country. It does not matter if you are going to a restaurant or any historical place, there is always a chance that you might have to get past a security checking area and it is important to show your documents. The Vietnamese authorities may also require you to submit your papers for random security checks.
Be sensitive about their experience of war
For a country like Vietnam, which has suffered a lot from war, you should not start chatting up locals about this touchy subject. In fact, you should show some sensitivity and try to share their burden. Of course, you cannot do much about the lives of millions which they have lost to war, but every effort counts and keeping this in mind, you must make an appropriate effort.
Follow the laws
No foreigner is exempt from the law and you must learn the basic rules and regulations of Vietnam before paying a visit.
You should make some effort to blend in with the Vietnamese culture. For this, you should move try dressing a little conservative with long pants and shirts.