Something else that goes along with Bogie's comments, is that you may have little choice in making "direct" eye contact. Depends on your reason and purpose for being where you are, and interacting with someone in the first place.
If you're dealing with someone, or a small group of several people that are less dominant to a single one among them, you may have little choice but to make and sustain eye contact with the dominant person, and occasional eye contect with the less dominant ones. Sometimes the failure to make eye contact is seen as an admission that YOU are admitting to being less dominant, and you're suddenly prey again ...
Naturally, this isn't anywhere near this simple ... but there are ways to establish a boundary of dominance without being considered overtly aggressive and challenging. Several books written back in the 60's & 70's ... like The Territorial Imperative ... give interesting glimpses into our nature, and the way our societal interactions are still affected by the way we were thousands of years ago ... Okay, and still are in many parts of the world, but we're not supposed to look at it that way, you know?
Just remember these things are ingrained somewhere very deeply inside us ... somewhere back in the lizard brain, as it were ...
And don't be distracted by the eye-contact game, and forget to watch the entire body language. Sometimes the body contact will, indeed, give away a pending physical action that the other person hasn't even realized has already been decided upon by that portion of their primal nature buried within them ... Don't get blind sided ...
If you are into practicing the softly focussed-yet-unfocussed awareness gaze, this is easier to prevent, as you're able to take in their entire body language and eye movement ... But don't expect it happen over night. Not deliberately, anyway ... although your buried nature may bring it out and use it in times of life & death situations ... and without your conscious mind ever being aware of it, or being able to remember what it was that keyed you to the action a second before it occurred.