I can tell you about Australia, I believe it is similar to America. Be careful what you do with your hands. You must not place your hands on the persons waist or below, that is considered intimate. It is probably best not to make any real contact with your hands, except perhaps for the shoulders, and the upper back. Most of the pressure in the hug will come from your arms, not your hands. A hug should not be too quick (like you want to finish it soon) nor should it be too long (so that the person wonders what you are doing). About 2-3 seconds is good if you are wanting to be very friendly, less if you are just being polite. Females often kiss other females lightly on one cheek, and males could do this too, if a cheek is offered. In Australia, males kissing males is to be avoided, that custom is for Europe. A kiss could come before or after the hug, depending on whether the cheek is offered. This kind of greeting would be more common when meeting older females. Tells us about hugs in China, I am interested!

Definitely, American's hug is different from ours.I mean their hug sometimes just means 'Hi, it's good to see you here'