In addition to hunting, I do a lot of glassing as a Range Safety Officer. My company does long range ballistics work on private land that is bordered by BLM land. I'm usually the RSO and shooter. In this case, I'm looking for any type of mammal that could wander onto the range. In addition to looking down range, I also check my six o'clock periodically Distance varies up to about 1.5 miles I use a bino, spotting scope and rifle scope.
I use a straight eyepiece spotting scope and raise it up off the ground to reduce turbulence-induced blur and to get a comfortable viewing position. I divide the field of fire into reasonable size scan areas, usually only ~15 degrees wide. I use a step scan method to scan each area, shifting the scope 1/2 of the field of view at a time. I scan left to right like reading text, which minimizes focus changes
I find that taking frequent rests helps a lot. Terrain starts to look like wallpaper after 10-15 min of study. That's a good time to take a break, get some water, check my six, switch optics, etc.
If you want to know how effective your glassing is, go over the area once using a visual scope, and then repeat using a thermal scope. I am often stunned at what I missed the first time. I use the highest contrast glass I can find to improve my chances of detecting visually.