Man greeting Man - Men shake hands when greeting one another while maintaining direct eye contact.  A firm but fairly brief handshake is the norm. With friends, a simple hello will suffice.  If you have not seen someone in a long time, a hug is common. 

Woman greeting Woman- At a first meeting, women generally shake hands while maintaining direct eye contact. With friends, a simple hello will suffice.  If you have not seen someone in a long time, a hug is common. 

Man greeting Woman- At a first meeting a regular handshake will do. Good friends may engage in a light hug or a single cheek kiss.