Kiss (not your OH)

Right ladies and gents. One cheek, two, or three times for greeting kisses??? I never know. If she is a close friend it's full on, someone you know and is comfortable with 50/50 like half of your lips meeting. That takes away the problem - but with people you don't really know? I always let the female take the lead and obviously with certain countries you know its two anyway, but how do you approach it??