Non-Verbal communication and some differences in Non-verbal communication of Viet Nam and America

ouch
eye contact (gaze)
volume
vocal nuance
proximity
gestures
facial expression, pause (silence)
intonation
dress
posture
smell
word choice and syntax
sounds (paralanguage)
Broadly speaking, there are two basic categories of non-verbal language:         nonverbal messages produced by the body;         nonverbal messages produced by the broad setting (time, space, silence)
Why is non-verbal communication important? 
Basically, it is one of the key aspects of communication (and especially important in a high-context culture).  It has multiple functions: 
Used to repeat the verbal message (e.g. point in a direction while stating directions.
Often used to accent a verbal message. (e.g. verbal tone indicates the actual meaning of the specific words).
Often complement the verbal message but also may contradict.  E.g.: a nod reinforces a positive message (among Americans); a “wink” may contradict a stated positive message.
Regulate interactions (non-verbal cues covey when the other person should speak or not speak).
May substitute for the verbal message (especially if it is blocked by noise, interruption, etc) — i.e. gestures (finger to lips to indicate need for quiet), facial expressions (i.e. a nod instead of a yes).
Note the implications of the proverb: “Actions speak louder than words.”  In essence, this underscores the importance of non-verbal communication.  Non-verbal communication is especially significant in intercultural situations. Probably non-verbal differences account for typical difficulties in communicating.
3, Some differences in Non-verbal communication of Viet Nam and America
Gestures
Impossible to catalog them all.  But need to recognize: 1) incredible possibility and variety and 2) that an acceptable in one’s own culture may be offensive in another.  In addition, amount of gesturing varies from culture to culture.  Some cultures are animated; other restrained.  Restrained cultures often feel animated cultures lack manners and overall restraint.  Animated cultures often feel restrained cultures lack emotion or interest. 
Even simple things like using hands to point and count differ. 
In US:
Americans will often wave to another person and then turn to make hand scoop inward; or raise the index finger ) palm toward one's face, and make a "curling " motion with that finger means to beckon or summon another person.
Arm raised and the open hand "waggles" back and forth means Signaling "hello" or "good-bye." Or trying to get someone's attention.
Palm facing out with the index and middle fingers displayed in the shape of a "V."- "Victory" or "peace."
Thumb and forefinger form a circle with the other three fingers splayed upward; it is used frequently and enthusiastically. "O.K." meaning "fine" or "yes."
Thumb up with a close fist means support or approval, "O.K." or "Good Going!" or "Good job!"
Fist raised with index finger and little finger extended. Texas rallying call "hook 'em horns." Baseball meaning "two outs." 
Extend the forefinger and make a circular motion near the temple or ear. Something or someone is "crazy."
In Viet Nam:
Custom of shaking hands is the customary form of greeting, but often nod of the head or slight bow is sufficient. 
Waving hands is not really common with old people in Viet Nam, but opposite to young people , wave hands is very common and friendly way when say goodbye to their friends.
Thumb and forefinger form a circle with the other three fingers splayed upward also used by Vietnamese people to give signal or it mean "good", "great"… 
"V" showed by forefinger and middle finger mean "victory" or "hi", "hello"
General Appearance and Dress
All cultures are concerned for how they look and make judgements based on looks and dress. 
America: 
 Americans appear almost obsessed with dress and personal attractiveness. Consider differing cultural standards on what is attractive in dress and on what constitutes modesty. 
Attending to a wedding, Women like to wear bright or colourful dress. Popularly, Men choose comple.
America often wear dark or black stuffs when they take part in an one's funeral.
Viet Nam:
There are 54 ethnic groups in Viet Nam. Each of them have their own dress style, for instance, women of Gia Rai group usually wear nothing but a small skirt, and men would take just a loin-cloth to go on any occasion. On special times like tet days, The H'Mông girls wear a shirt, undergarments, leggings and put on a coiled scarf on their head. Their skirts are usually in cone shape with lots of folds that enhance their gentleness.People of the subgroups in the Dao minority share many similarities while at the same time are a little bit distinct from each other. Girls in the Dao Đỏ (Red Dao) keep their hair long and fold them around their heads covered with a red cloth. They wear indigo dress embroiled with decorations in red…
In wedding Kinh ethnic (Viet people) wear bright clothes and bless bride and groom happily. In contrast, Vietnameses often clothe dark or black stuffs in one's funeral to show their respectation to the death and sympathy with dead's family members. Dead's son/daughter wear a weeper on forehead and a small long white cloth to go into mouring their dad/mom or grand mother/ father.
Posture
Consider the following actions and note cultural differences: 
Bowing : American people do not make their bow to their partner because in American culture bowing is a sign of submission, the admission that another person is superior to you. But incontrast Vietnamese young people usually make their bow to older people when greeting expressing respect to old people.
Sitting with legs crossed : in Viet Nam, it is acceptable to sit with you legs crossed when you meet your friends or peer people. Eventually, in a meal including young and old persons, guys can sit with legs crossed, it's acceptable. To Americans, male sit crosses at the ankles; rest ankle of one leg on top of the knee of the other leg; some cross the legs at the knees.  female sit crosses the legs at the knees; crosses the legs at the knees and curls the upper foot around the calf of the lower leg.
Facial Expressions
While some say that facial expressions are identical, meaning attached to them differs.  Majority opinion is that these do have similar meanings world-wide with respect to smiling, crying, or showing anger, sorrow, or disgust.  However, the intensity varies from culture to culture.  Note the following: 
Viet Nam:
People exaggerate grief or sadness.
U.S:
Most American men hide grief or sorrow.
Eye Contact and Gaze
In USA:
Eye contact indicates: degree of attention or interest, influences attitude change or persuasion, regulates interaction, communicates emotion, defines power and status, and has a central role in managing impressions of others. 
American children are taught to look others directly in the eyes meaning when greeting and conversing. If not, means shyness or weakness. African-Americans use more eye contact when talking and less when listening with reverse true for Anglo Americans.  This is a possible cause for some sense of unease between races in US.  A prolonged gaze is often seen as a sign of sexual interest.
In Viet Nam:
Direct eye contact and staring is uncommon in those areas accustomed to foreign visitors. However, in smaller communities, visitors may be the subject of much curiosity and therefore you may notice some stares. But when speaking face to face to a person, you should use derect eyes to show your respect and truthfulness.
Touch
Question: Why do we touch, where do we touch, and what meanings do we assign when someone else touches us? 
Basic answer:  Touch is culturally determined!  But each culture has a clear concept of what parts of the body one may not touch.  Basic message of touch is to affect or control  — protect, support, disapprove (i.e. hug, kiss, hit, kick).   
In U.S:
Handshake is common (even for strangers) in U.S. Shake hands is a polite way to greeting. At early age they are taught to do so with a firm, solid grip When greeting one another.
Giving hugs, kisses for members of family or relative or friends is on an increasingly more intimate basis. 
Native Hawaiians hug and exchange breaths in a custom called "aha."
Most African Americans touch on greeting but are annoyed if touched on the head (good boy, good girl overtones).
Americans see that is very weird if people of the same sex hold hands in public places.
Personal space becomes much larger; people are not as comfortable when others stand close to them, especially if they are not very well acquainted.
In Viet Nam:
Touching one's head means impolite but with children that action express encourage them. But a special reason is Asians' thought Head houses the soul and a touch puts it in jeopardy. 
Hugging and kissing when greeting are uncommon. Especially, in public it's unacceptable to display of affection like kiss or hug or any action that too affectionate.
People of the same sex may be seen holding hands in public places, which is simply a gesture of friendship.
If 2 people meet the first time they keep the distain not too far but not so closely. But when 2 people are friends or relative , they stand close or touch to each other.
Cultures (English , German, Scandinavian, Chinese, Japanese) with high emotional restraint concepts have little public touch; those which encourage emotion (Latino, Middle-East, Jewish) accept frequent touches. 
Conclusion
To sum up, As the global village continues to shrink and cultures collide, it is essential for all of us to become more sensitive, more aware, and more observant to the myriad motions, gestures, and body language that surround us each day. And as many of us cross over cultural borders, it would be fitting for us to respect, learn, and understand more about the effective, yet powerful "silent language" of body language. 
References
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