Go to The State Building located at Post Code 506 and apply for the garbage collector job. From there you can go to the Garbage Depot located at Post Code 385 to request a route from the supervisor. After you request your route, you will be issued a garbage truck. Drive the route using your GPS and garbage truck to collect garbage at various locations around Los Santos. When you have completed the route, return the garbage truck to the Garbage Depot and Collect Paycheck from the supervisor.