• Add lighting around the unit

Thieves aren't looking to get caught, obviously no arguing on that point.  The more visible they are or inaccessible the unit is during the heist the less likely they will bother your home or office.

• Add Security Camera's near the unit

Not a full proof way but again under the same principles as before.  If they know they are being watched they are less likely to do it AND/OR they are more likely to get caught after the fact.

• Apply Unit Fence or Cage

Of all the options this is probably the most full proof.  Thieves will typically just move onto the next unit that will be much easier than yours.  You can either buy pre-fab cages OR you can have them customer made by an ironworks company.  If someone makes you a cage be absolutely certain that the unit can STILL BREATH.  If you restrict airflow or allow build up of leaves and debris the unit will suffocate and not operate efficiently.  Always consult an ac professional if you are at all uncertain.

• Lock all Property Gates or Fences to prevent easy access throughout the property.

This can easily be overlooked.  Make sure your access points are locked tight when not in use!

• Remove or Secure Ladders to decks or roofs.  

This typically applies to office buildings.  Rooftop package units are stolen when the AC system is easily accessible.  Don't make it any easier on the thieves than it needs to be.