Truth be told, I do this at times and I'm only looking for ONE of TWO things, Absolute Comfort or Glimmers of Panic, most often seen in their pulse rate in the neck (as compared to my feeling of my own under the table on my wrist) and through color changes in the face. I personally pay little attention to any
tells around the mouth b/c they are the most often fainted.
For all you new to live poker, remember the above, it comes from a very profitable live player who now makes a living on the felt. (Not a pro, I love my family time too much) : )