Instructions
Drive normally until you encounter a police car. The cops must see you commit an infraction before they'll give chase.
Drive off the road, crash into a sign, collide with a civilian vehicle or ram a police car to commit your first infraction. Any police in the area will sound their sirens and begin to chase you.
Escape from the police to commit future infractions. Reaching a very high speed while being chased will also register as an infraction --- 150 mph counts as speeding, 180 as excessive speeding and 200 as reckless driving.