Unfortunately, these efforts can also draw in thieves, arsonists and squatters, so approach it by putting security (and safety) before attractive aesthetics.
Measures required for each site will be unique – there may be limitations to what’s possible. For example, you can’t put a fence up on the pavement in front of a mid-terrace high street shop. On the other hand, additional measures may be needed if a specific vulnerability is identified, such as being located on an out-of-town industrial estate that is largely deserted at night, or where there is a high risk associated with unauthorised vehicles getting on the site.
Various types of perimeter and building defences are outlined below, but this isn’t an exhaustive list of what can or should be put in place.