Security fencing is the best form of perimeter protection - and exits and entrances should be kept to a minimum. It is best to place the Reception Area near the main gate and you could also consider employing security guards. Companies working in areas where there is good natural surveillance may find it better to use the weld mesh-type fencing panels rather than the solid boarded type - which would enable the public to report anything that looks suspicious.
Other obvious safeguards are:
If such safeguards are not possible it is even more important that building schedules are up to date, that they clearly show when new contractors are expected and when materials are arriving. This means that you can look out for, and challenge, any unfamiliar person on site.
