For commercial and custom knives, the first thing that I do is to just hold it and get a feel for it. I enjoy looking things over carefully and appreciating the beauty of the design.

The next thing is to feel how the handles are fit to the tang (if it is so designed). If it feels smooth with no sharp or raised edges I move on from there. If the fit is a little sloppy, my interest begins to wane.  

Military knives and bayonets are another issue. I just appreciate the feel and imagine how they were designed to be used. I appreciate them for what they are and not necessarily for how exceptionally they are constructed.