Have a look at this TED talk by Amy Cuddy. Cuddy is an American social psychologist known for her research on stereotyping and discrimination, emotions, power, nonverbal behavior, and the effects of social stimuli on hormone levels. This talk about body language is very insightful or at the least it should get you evaluating the social cues good or bad you have been subconsciously sending to others.
This talk also reminds me of a book I read some time ago, What Every Body Is Saying: An Ex-FBI Agent’s Guide to Speed-Reading People, if you have the time you should read it as well. The author Joe Navarro was a career FBI agent specializing in nonverbal communications, in his book he systematically explains human behaviors and how to read what people are actually saying to us via their body language.