I look for two things, sticky bolt and extractor marks. I used to get flattening or cratering primers with relatively light loads, and because of that I don't use primers as a sign of pressure (unless its a blown primer of course). depending on the cartridge, I may get extractor marks before sticky bolt lift, or the other way around, but as soon as I get one I back it down by .5gr and use that as my max possible load, then I look at my targets to see where the accuracy nodes are and work from there.