The concept of dogwhistling is relatively new to me, so i can't specify cues about that.
However, you can notice cues about deceptive or manipulative behavior:
Also, is important to notice that while there are some cues of concealing behavior, not every person have the exact same cues. For example, while some people avoid eye contact while lying, others actually increase it. Context is also important, sometimes people are just nervous or umconfortable.
It takes some degree of familiarity with the person. (seeing them through a screen enough times counts) You need to figure their base body language. When you are familiar with that, you can tell how they feel about a subject and how comfortable they are talking about it or if they are concealing /avoiding something.
Is not like this show "Lie to me" where every person scratching their ear was a liar XD
This may be a tangent, but if you are interested in studying body language, i recommend you the book "what every body is saying". The author Joe Navarro is an ex FBI agent, so he had to familiarize himself with deceptive behavior and how to notice it.