CCTV cameras in city centres are successful deterrents, but the knock-on effect is that criminals target premises further out of town that are not under surveillance. Installing your own exterior CCTV cameras is expensive - about 5,000 to install and around 100 a month to monitor. Cameras inside your office are cheaper but less effective than on the outside because intruders will probably be wearing balaclavas so they can't be identified. Flooding the scene with light when an alarm is activated can give intruders a fright. They will feel horribly exposed in an otherwise dark street and may take to their heels.
Bells ringing have the same effect.
Postcode all your equipment. One option is to use a stencil that burns into the plastic of keyboards and other hardware. Another is to mark equipment with an indelible marker pen whose ink is only seen under an ultra violet light - available from office stationers. One victim of ten break-ins now has three deadbolts and is considering reinforced door hinges to prevent the door from being broken down. If you install laminated glass, which is the stuff of modern windscreens and incredibly strong, it is hard to shatter.