I have several rifles and pistols. I also shoot a lot, so i have a large "main" box with files, jags, flints, caps, patches, wads, powder measure, ball starter, tools, and etc. That box goes to the range every time. It consists of several of the clear tackle box, containers.
I have a large assortment of range rods. Mostly steel with brass muzzle guards. Small ones for .32 cal. and long ones for Long Riles and etc.
I have several plastic boxes (tool boxes) for individual calibers. Special box for smooth bores and special boxes for pistols, and powder.
I have a small utility vehicle, that I keep spotting scope, targets, staplers, rags, shooting rests and etc., in.
In my shop, on the wall, I have a poster board with a check sheet, that I review, prior to going to the range.
Then after all that, I usually forget something...like the gun, for instance.