Assuming that a generous exposure has been given for the shadow areas of the subject, the main purpose of inspection development is to avoid overdeveloping the negative. The secondary purpose is to avoid underdevelopment. With the latter in mind, remember that the emulsion side of most properly developed negatives will appear too dark under the safelight, so it is best to judge by the base side. The most usual advice for negative inspectors is to pull the negative from the developer when the highlights appear as substantial black in the general milkiness of the base side. To guard against underdevelopment, you can look for some evidence of density in zones III or IV on the emulsion side, but you must remember it will be minimal.
Experience is the best judge.
Above are two negatives developed by inspection. Push and pull processing should usually be done by the time and temperature method only. Negatives of very high contrast subjects, which require overexposure and underdevelopment, also present unique difficulties, since they often appear too dense on the emulsion side and not dense enough on the base. Typically, a high contrast negative will show detail on the emulsion side early, but will still require further development to provide sufficient shadow detail. Negatives developed in pyrogallol or pyrocatechin are particularly suitable for development by inspection the tanning effect these developing agents have on photographic emulsions desensitizes them somewhat to further exposure.