Pimp My Ride - Unlockable customers

Unlock Alyana, Jason, and Sandra:
Pimp out Hari, Leon, and Alixs ride

Unlock Hari, Leon, and Alix:
Pimp out Marias and Andreas ride

Better score:
Most of the time the kind of things in most need of pimping are usually body kits, paint jobs, and rims. Go for them first to get a better score.