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 often suffice.  

Woman greeting Woman- At a first meeting, women generally shake hands while maintaining direct eye contact. Between good friends and family a light hug and exchanging kisses on one or both cheeks is common.  The kisses are more like air kisses, touching cheeks instead of kissing with the lips.

Greeting between Men & Women - At a first meeting a regular handshake will do. It is usually best to wait for the women to initiate. Between good friends and family a light hug and exchanging kisses on one or both cheeks is common. The kisses are more like air kisses, touching cheeks instead of kissing with the lips.

Note: Austrians tend to say “Gruss Gott” in formal circumstances and “Gruss Dich” in more casual situations. The latter is like saying hello when you walk into a shop or pass someone you know on the way.