I always check for play in the blade and lock. Some always develops in use, so I want as little as possible to start off with. Matching scales next. They don't have to be perfect, but I don't like a real light one and a real dark one paired together, it has to be one or another. Last but not least is how the blade is ground. I don't know what it is but lately they are coming with almost a small re-curve area near the tang. I hate that, I want the edge straight all the way back. It's gotten to the point that I won't even buy one w/o seeing that area first. I sent my 172 in a little while ago to have a small nick removed and that's the way it came back, grrr.