Advertise on your vehicle. And your other vehicle. And anyone else that will let you put a door magnet on. Up until recently, that is how I always found someone. Word of mouth will take over once you begin to provide quality service.
I don't know what you drive, but try to look at it from a customer's perspective. If you drive a H2 or new crew diesel and a 16' enclosed, I know I will be paying alot for my yard for you to get around in that, no matter the quality. And if you drive a 1980 Chevy with rusted fenders so I can see THROUGH the bed to the other side, I will figure my yard will be hacked.
Neat and clean....just like someone wants their yard.
Maintain the quality of service and you will retain the customer.