Stick to the basics.
Too many people applying for PSS roles get bogged down in the detail of the latest and greatest technology on the market but don't display an in depth knowledge of base security theory. I couldn't tell you what the name of the latest CCTV, EACS, rising step or locking mechanism is - but I could tell the functionality I require from it.
Showing a prospective employer that you have a firm grounding in the basics is key. Areas I look for people to demonstrate include their knowledge of 3DR (Detect, Deter, Delay and Response), CPTED, Defense in Depth and concentration of assets type theories. Also linking the prescription of physical security treatments to identified risks and demonstrating an understanding of security risk management is a great advantage.