Or at least how I do it.........Arrowsong ask on another thread about aiming and shooting at different distances - instead of burying it there I thought a new thread would be in order. Now I am no expert, but I have found a method that is pretty easy to do and works for me - I did not come up with it and do not claim as much and if it works for you great, if not that's fine too.
To set my gaps I like to take a piece of masking tape about 3' long and place it on the target butt vertically. Then I like to add cross pieces about 6" long at about 8" intervals so I have a vertical line with several cross pieces. I start off at 10 yards, pre-aiming at the top X as described in a prior post - draw back, make note of where the point intersects the vertical tape mark, then focus back on the top X and execute the shot. I'll take several shots until I am confident that the group is representative. Then I write down the measurement and move back 5 yards and repeat until I have marks to 40 yards my point on distance. Beyond that the same concept works but you hold over instead of under.
I shoot 3 under with a middle finger to corner of mouth anchor. A higher would reduce gaps, lower will increase them.
Now here's the good part about knowing and having smallish gaps: My gaps are 16"@10yds, 20"@15yds, 24"@20yds, 20"@25yds, 8"@35 and Point on at 40.
As you can see from 15-25 yards are nearly the same gap - and also the most common distances for hunting and at most 3D's.
Now here's the good part - most deer/antelope etc 3D targets as well as live critters are approximately 24" from center of the kill zone to their feet. Now if we put all this together any shot at a standing deer etc at 15-25yards, I will pre aim centered on the critter, draw back - check the gap (point at the feet) focus on the spot I want to hit and execute the shot. You will obviously have to adjust for your own gaps and different targets and ranges, but hopefully you get the idea.
None of it's any good if your form is inconsistent, but if your shooting good groups then this may help with some of the range estimation/shooting issues.