Here is my method for a 3D course...let's say for a 33 yd shot.
1) Is it over or under 30 yd based on my first impression.
2) Where is the halfway point. What is that distance? Over 15yd less than 17yd. So full distance should be 30 to 34 yds.
3) Take ten yard increments...1, 2, 3, plus about 2 to 4 yds...so we are about 32 to 34 yds.
4) Shoot the shot for 34. High ten. Check with rangefinder, 33 yd.

This method is pretty effective in most situations on level ground. But from a treestand, I find things look further to me than the horizontal distance, which is what dictates which pin to use. Am I hurting myself by doing 90% of my field judging practice from the ground?