Some of it is mind set, some of it is tactics, some of it is knowledge, a lot of it is practice.

Like mind set. For a very long time, our ancestors were not at the top of the food chain. Meaning there were lots of saber tooth type critter out there trying to make a meal out of humans. Those humans who were good at spotting danger first, could avoid it, and survive. Those who failed ended up being predator poop. So after millions of years of this, our brains are hard wired to spot danger. Now, humans also are hunters, and hunters have a very distinct way of moving. Subconsciously, people are looking for, and will notice "hunter/predator" type movements before they notice any other kind of movement. This also applies to other animals. Go out deer hunting, and if you move in long straight lines of travel, at a steady pace, the deer will pick up on that quickly, and be gone. So avoid moving like a predator on the hunt.

Tactics, use basic camouflage. Shape, shadow, shine, silhouette, shading. Human form is very distinct, break up the outline and your harder to see. Why do you think field uniforms look so baggy. Shadow, stay in them, use them to your advantage. Use them to detect others. Shine, ca-mo up anything that shines, including skin. Silhouette, is basically not sky lining yourself. You can also use this to detect people too. Picture a dark field at night, your walking along, hear something, but can't see it. Lower your head to near ground level, and sky light the target. Dogs often will lower their heads when trying to see something better. Shading is just using the right color or shade of camouflage to blend into the background. Also, when a well camouflaged person is still and can not be seen, and they move, did you know the first thing the human eye see's moving is the color black? That's why new camouflage uniforms have eliminated the color black. It is also why all black uniforms really are not great at night. Dark grey, even purple is better.

Knowledge, you have seen some of it already. the stuff like humans see black moving first, sky lighting tricks, ect. Basically, study how humans detect, and how to counter that detection. Humans detect visually, but also by use of sound, smell. Also, sixth sense. Really, have you ever stared at someone, and they turned around and looked at you? Have you ever for some unknown reason turned around and looked at someone who was starring at you? So, do not stare right at someone, use off set vision.

But the big thing is practice, practice, practice. Camo up, go out into the woods, and hunt each other with paintball guns. Pain is a great motivator to teach you what you did wrong. But make sure you debrief each other about how, and why you saw the other person.

Anyways, be safe, have fun. Remember, sometimes looking and acting suspicious at the wrong time, in the wrong place, even if your just playing around, can get you unwanted police attention.