For rifles, I bought some Alt-C qualification targets and started shooting at them at 25m with my AR and .22LR rifle in the various positions. I did some reading about how the Marines qualify versus the Army and decided I needed to modify the target to be a bit more challenging. I cut one up, scaled the 250m target to 50% to make a 500m target, and made a bunch of copies of targets ranged 150m, 200m, 250m, 300m, 500m.
I shoot at each, again set up at 25m, in the following order:
Standing - 150m / 200m
Kneeling - 200m / 250m
Sitting - 250m / 300m
Prone - 300m / 500m
I can usually get between 70-80% hits overall, sometimes better, though sometimes I have a bad day. Note this is with iron sights only - when I put optics on / go supported, I add 50-150m to each range stated above.
I've found that shooting at scaled targets is much more efficient than actually walking to the 50 / 100m line every time I want to change targets, plus I can usually see if I've missed from the line. Being so close, practice with my .22LR is handy and affordable, too.
My goal overall is to be a well-rounded marksman, able to realistically hit at the maximum effective range of my weapon (AR in .223) and do so from field positions. I only set up on a bench for work-ups or zeroing.
For reference, if the average man stands approximately 20" across the shoulders, then a simulated 100m target at 25m would be 5" across the shoulders. A 200m target would be 2.5", a 500m target would be 1", etc. I've since printed all different sizes to represent everything from 50m - 600m targets at 25m, 50m, and 100m.
Also, having all these targets on 8.5x11 paper (or 11x17 if I want a big series) is cheap and easy to carry to the range, and I can duplicate whenever I want on a copier.
Note - I would LOVE to be able to shoot at actual targets from 200-500m, but my range only goes to 100m, so scaled targets is the best I can do at the moment.