Not take them in the first place, develop them at home or a private lab, or use Polaroids.

I worked in a photography store in Italy in the summer 30 years ago or so. That's not always what was happening.

Neither I nor anyone else working there ever looked at anyone's private pictures, but the guy delivering them from the lab would sometimes joke about or allude to customers' photos, always from some other store. Even as a kid, I found that troubling. It also made me wonder what he told other stores about our clients' pictures.