Make certain that you have an up-to-date record of all keyholders.  

Make daily deposits, never leaving large amounts of cash on the premise.

Never allow one person to close and secure the business.

Keep window signs at a minimum to avoid blocking the view from the outside.

In retail establishments, make sure that exits are marked with height indicators.

Make certain that financial records and checkbooks are in locked areas, secure from employees.

Always be on the alert for any financial flags; investigate them thoroughly.

In large businesses and partnerships, adopt a two-signature check system.

In corporations or organizations, the person processing checks should not be the same individual who first receives and records the cancelled checks.

Perform background checks on all employees and photograph them.   Maintain copies of all employee driver's licenses.

Consider the installation of an electronic security and fire alarm system.   Review options for video surveillance and access control systems.

Security systems should be code operated, not key operated.   All users should have different access codes.

If using an automated payroll system, do not have blank checks in a printer accessible to unauthorized personnel.

Make sure that all critical accounting software is password protected.