I never pay too much attention. If I go to a fitting I am relying on the fitter to watch me hit, my numbers including things like angle of attack and dynamic loft and adjust the shaft accordingly. We will have a conversation about what suits my eye, usually a mid-flight and in a driver trying to keep spin off.
If I am testing off the rack I'll simply look at distance and dispersion with the stock shaft and then those I am offered. Choice will probably be limited to a few stock options in different flexes. As long as I am seeing some more distance ideally but particularly tighter dispersion then it gives me something to work with and consider.