Man greeting Man - Men shake hands when greeting one another and usually maintain direct eye contact.  Handshakes may linger.  Good friends and family will engage in a firm hug which may be combined with a few slaps on the back. 

Woman greeting Woman - At a first meeting, women generally shake hands.  Friends and close acquaintances kiss each other once on the cheek. 

Man greeting Woman - At a first meeting a regular handshake will do.  Friends, family and close acquaintances usually share a light kiss on the cheek.