When introductions take place, shaking hands is also customary, but much depends on the formality of the situation and individual preference. Handshakes are firm and brief. In conversations, Americans generally do not touch each other as casually and frequently as people in other cultures do. Of course, close friends will often hug when greeting or saying goodbye.
This was another differnece I could find in American dramas or television shows. Generally, Korean people(especially females) tend to touch each other and sometimes even hold hands together as a reflection of close relationship. However, I heard from my American friends that they were really surprised and frustrated to see Korean people making a lot of hand motions and other gestures that included teaching each other's hands or other parts of the body. Koreans are relatively less offended by such motions or actions than Americans I believe.