“Maximize depth of field” advocates the smallest aperture, e.g., f/22, “to ensure maximum sharpness throughout the entire scene.” But diffraction effects decrease image sharpness at small apertures. Use the largest ‘smallest’ aperture giving the required depth of field to truly get maximum sharpness. Related to this and to best set focus for hyperfocal distance (“Getting hyper about focusing”), be aware that lens barrel depth of field marks (if your lens has them) are for guidance for “typical” enlargement size. If you print / view larger than about 8”x10” you need to use a smaller aperture than indicated. Maybe that’s why Ian Shire advocated a generic f/22 in the first place.