Ways to unlock customers
     Pimp out a few customers rides to get more customers:

Unlock Hari, Leon, and Alix as customers:
     Pimp Maria's and Andrea's ride.

Unlock Alyana, Jason, and Sandra as customers:
     Pimp Leon's, Hari's, and Alix's ride.

Higher score:
     Most  of  the time the kind of things in most need of pimping are
usually  rims,  body  kits,  paint  jobs. Go for them first to reach a
higher score.