Pick up Liv, drive her to the Coit Tower roundabout, and then follow her crazy GPS route through town. Launch high off ramps, gaining maximum air as you go. Constantly check your minimap to see corners coming up.
Choose a vehicle that has good stability when cornering and landing. Remember to right the car in the air so it lands on all four wheels. When the daredevil jumping begins, your rating is one, but this increases the more air you get. Therefore, line up each ramp, boost, and land properly to ensure a five-star rating. Also gain extra air by boosting over hilly road junctions.