Regular testing, auditing, and rehearsal of your disaster recovery plans are essential to make sure that they do work, and can be progressively refined to cope with any changes in your work requirements.
A common problem is where the backup portion of the plan is tested, but not the restoration process. Only during an actual disaster are problems with the restoration process discovered.
Departmental managers should budget for staff time and expenses to perform regular full rehearsals of the disaster recovery plan.