I do it a bit backwards than most, but it is still a type of ladder test. I am of the opinion that each gun has a best "off the lands" depth that affects groups more than powder itself. I will always load sets of rounds set at different distances off of the lands. I usually start with .02, .04, and .06 off of the lands loads all with the exact same powder and charge weight (and always trickle to get exact charges). I typically use whichever powder the books show as the most accurate in their tests if I have it. I will then shoot these loads and determine which distance off the lands my rifle likes best. There is usually one obvious group.
I will then start with ladder tests of two or three different powders and charge weights depending on the caliber. Typically, I do two, three shot groups for each powder load. One powder will then usually show as the best option for that particular bullet. From there you can do a second test with just the one powder if you really want to get exact. For Hunting purposes, I am usually good after my three shot group testing.