Continued compliance with the spirit of this credit is largely based on the honor system and the integrity of building management and users. To ensure that preferred parking policies are respected, consider the following strategies:

Wherever preferred parking is provided, post signage that identifies preferred parking or alternative-fuel stations.
Signage can be as noticeable or discreet as desired, but must clearly demarcate preferred spaces as such. 
A sticker program can be implemented to identify cars that qualify to park in preferred parking spaces. 
Provide information about the parking program via appropriate channels for your project.
Post information about the parking program in entryways and in public areas.