From "Basic Military Handbook" Army Service Forces Training Center, Camp Lee Virginia, 1 Feb 1945
The ability to pick up indistinct moving objects may be acquired by practice without the necessity of a system of searching, since the eye is naturally attracted to moving things. But to pick out motionless objects requires systematic search. The scout searches the ground in belts or zones parallel to the front, at successively increasing ranges, within his range of vision. He begins with the zone nearest him, searching the belt systematically from right to left, omitting no portion of it. The places where an enemy might be concealed hold his eye longer than open spaces. In this manner, with his eye properly focussed, he searches all places at the same range. He then proceeds to another belt farther out, but overlapping the first, and searches back from left to right, and thus procees until he has thoroughly examined all terrain to the front and well to the flanks within his range of vision. This search is made with the naked eye. If he is equipped with field glasses, he uses them for close examination of any localities that appear suspicious.