Deviant Ollam did an amazing presentation on his work as a penetration expert. He goes over how they do their work finding the weak points in buildings and companies.

He goes over common door penetration topics: fitment issues, bad latches, opening tools, etc. He also covers lots of topics like duplicating keys from photos, rental key boxes, learning everything you need for faking a service call from service provider key boxes, circumventing buzz-in door boxes or gate access systems, RFID lifting, issues with camera systems, criminally available master keys for common doors/locks.