I have lots and lots on INTPs and ENTPs to study so they tend to be pretty easy for me to pick up on. Plus I travel to tech heavy cities so they planes tend to have a lot of NTs on them. If you combine styles and patterns of dressing with the eye movements and just the general attitude they entps just sort of pop out.
A friend had went to a few nlp classes and we started watching eye movements after that.
Entps will alternate upwards-right or upwards-left movements when in a super Ne state with very direct, focused, studious stares when using a lot of Ti. They tend to alternate. If not having to focus a lot this means lots of focused glancing.
INTPs tend to be looking directly but not really at you, unless you can make them laugh about something and you can see the Ne start to kick in a bit. and they will be more active with some upwards glancing.
ENTJs stare you down like tigers and nothing is more fun than going head to head with an entj when you are right. They are very active and assertive and I luv poking them and making them twitch. They look mean and look agressive and assertive and have very direct, piercing eye contact with animation in thier facial muscles implying they will deal with you as needed.
INTJs look directly at you and it feels very intense but I think it is more like flat-panned. They are really focused on an internal order of things and once you get them to laugh, then you can see something activate in thier expression and the gaze relaxes a bit. Thier face itself -the muscles and such dont seem to have expression when in the flat-panned look