Man greeting Man - Men shake hands when greeting one another and maintain direct eye contact.  A relatively firm handshake is the way to go.  Light hugs are common between good friends and family. 

Woman greeting Woman- At a first meeting, a light handshake will suffice.  Light hugs are common between good friends and family.

Man greeting Woman-   At a first meeting a regular handshake will do.  Light hugs are common between good friends and family.

Note: When Americans say "Hi, how are you?", they are only expecting a "Fine," or a "Fine, thank you" or a "Good" in response.  It is not usually an invitation to a lengthy conversation.