Allan Pease, wrote an excellent books body language that was quite informative and yet not totally correct. It Vera Birkenbihls book that confirmed my observation that there is more to it than a few signals listed in a book.
Vera Birkenbihl more or less advises... make sure you take into consideration all the cues, consider local conventions, dress codes add to that tonal qualities. It comes down to observation. Unfortunately her book is only in german. I actually consider that book the best seeing it helps you to look for the cues but interpret them yourself.
Alex
