Well, I use a Sinclair concentricity gauge to measure runout. I think concentricity is one of the most important factors in accuracy and it's something I pay close attention to.

I usually neck size only and I use the Lee collet neck die for that. It's a great die with some distinct benefits. First, it works the neck less than conventional dies with expander buttons. Second, there's no need to lube your cases. And third, it makes very straight ammo whether you neck turn your brass or not and that's the main reason I use them. This die is not perfect, though. I've always found the tooling marks on the internal working parts to be excessive. But these can be easily polished away with some wet/dry sandpaper and oil. I also apply a little grease where the collet and collet sleeve bear against each other.

For seating I use either a Redding Competition seater or the Forster Ultra seater. I really can't find any fault with either one. Both have the micrometer adjustment which makes it easier to fine tune seating depth.

Since I started using the above combination, runout has been a nonexistent problem for me. I think the absolute worst I've measured is .004". Out of a batch of 20 rounds I'll usually have 4 or 5 that measure zero for all practical purposes. The rest will generally be in the .000 to .002" range. That's good enough for me.