Body language is common but different in different countries,it is important to know that,or we will be misunderstood.the handshake is a formal greeting,and you should shake hands with others firmly,because thes shows that you are friendly person,and as a friend,you may place your hand on others'shoulders,or greet your friends with a hug.
It is not polite either to stare at others or not to look the other person in the eye when you are talking,the former one make person uncomfortable,and the latter one means you are not interested or hiding something.
In America,you may make a movement with your hands as if you are signing a piece of paper to call the writer,it is all right to point at things but not at people with your index finger except to a child.You may scold a child by shaking your index finger or admire them by patting them on the head.However,the same gesture would has different meanings in different countries,and the smile is the safest thing
英语高手请进(帮忙翻译一下,谢谢)