The compounds are located in the nearby vicinity of the respective Airport. The distance is usually mentioned on their website. Book with a company whose compound is located on the minimal distance or add the fuel expense in your parking budget.
Go for the covered compounds. The open air ones will leave your car at the mercy of weather and birds. If you have chosen or had to choose the one with open air parking lot opt for the Valet Car Wash just in case.
Make sure that your vehicle is driven to and from the compound by the company appointed insured chauffeurs or Valets. Also ensure that your vehicle in parked inside the parking lot vicinity and only leaves the premises when it is to be returned to you. They any exceptions are required, do inquire about them.
The parking lot should be properly manned and guarded at all times. It should be equipped with all the standard security measures like proper lighting and steel fencing of the whole area.
Vigilant monitoring is the key to providing up-to the mark security. 24/7 surveillance and CCTV monitoring is the usual requisite for it. A complete record of your vehicle will ensure its 100% security.