I will place several targets in a horizontal line and shoot five shots at each one with a different charge weight. In accurate rifles, it is clear that some of the charge weights group together. I just did this for fun with a 223 and some 55 varmaggedons. From 24.4-24.9 grains there was a clear horiztal " streak " in there. I loaded a few more at 24.7 with different seating depths. They all shot under half an inch, and some under 3/8". It is a comfortable load with room for error.
This isn't the only way to do it. Robert Hoppes shoots 2 or 3 shot groups at 100 yards, takes the best load and tunes it at 600. I think his accomplishments speak for themselves.