The limits of one's peripheral vision may be determined in the following manner:
Stand erect with feet together, arms extended to the sides, (forming a "T"). Point the index finger toward the ceiling, look straight ahead and slowly bring bring the finger tips into view simultaneously on the left and the right.
The point where you first catch sight of your finger on each side is your peripheral vision on that side. The limit will vary with other people but, generally speaking, you should be able to see both fingers when your arms are extended out to the sides. Some degree of vision problems may be indicated if you have to bring your fingers more toward the center.

This diagram shows you the limits of peripheral vision with a little explanation.
To achieve this goal of "Out of sight, out of mind" first keep your attention on the back of the enemy's head. In this way you will be able to detect and predict the movements of his head and eyes. In order to be successful at this you must practice this every day.
Most movements are made in a calm manner, so someone who is quick should be able to stay out of sight. Once field of view has been made, keep LOW in your stance, remember that the enemy's shoulders block his side vision to some point.
Make sure you move SLOW when your in the area shown in the diagram, because a quick movement is likely to be seen out of the corner of the eye, therfore giving your position away.
Having gained a relatively secure position behind the enemy, out of his field of view, it is now possible to "check the trail" ahead by looking quickly in the direction you wish to go.
Once you see a clear path be sure it is free of obsticles and any other debris that might give your position away, again fix your attention on the enemy, keep this "RUN IN" as brief as possible, and you are in a position to move quickly if spoted.
Slowly, move around the outer limit of the enemy's field of view. Watch his eye from this vantage point. you will be surprised on how mush to you can tell on where a person is looking by watching him in this manner.
Perhaps the best way of passing the enemy without being spotted is to direct his attention elsewhere by throwing an object away from your position, any average size rock will do to draw the enemy's attention away from you.
From a hiding position throw a rock (or what ever object and without leading the enemy to your team mates position) over the enemy's head in such a way that it is not spotted in the air, but makes a loud enouggh sound to gain his attention in that direction.
Keep a low position during this movement, as you may be spotted by someone else without you knowing, and keep the movement of your throw slow and gently, even lightly. Such a movement is less likely to be seen. Remember cast the rock dont hurl it!

Remember!!