How else can security contribute to preparing for the worst?

All those involved with security know about the importance of learning from past events, but how good is the security sector at preparing in advance? What are the options to help prepare? To what extent are plans tested and what are the learning points? Major incidents such as terrorist attacks are mercifully rare, and there is guidance available on how to respond but how well practiced is the security sector and its clients? What priority is placed on security personnel being able to respond...