If you Choose to have CCTV, Get a good system. Avoid going with the lowest bidder; If you're called into court you need to show that you hired the best company not the cheapest.
Before cameras are installed Make sure the supplier lets you see the image from the proposed camera positions using different lenses.
If possible, have security personnel watch the video monitors around the vlock to catch problems as they happen. At the very least, record everything so you have evidence in case of a crime or accident.