I have written about this issue before and my answer is always observe, observe, observe.

Take a look around you. Observe non verbal communication. What body language do you see and other social cues. You may have to concentrate to notice them. What is the comfort zone of people (this changes from person to person and may dictate your own interaction with them). Now, most importantly, observe how other people react to such cues and communicate back in response to others. What is successful? What is not? Are there people you look up to or consider successful socially? Are you able to model their behaviours? I really don't know the exact percentage but it is safe to say that the majority of our social and communicative behavior is non-verbal.