Start by registering with KSS International, Inc. They are also known as Kern Scheduling. This is a scheduling company that is known as the premier recruiting and scheduling company. KSS schedules for over 60 different mystery shopping companies. They schedule tens of thousands of shops monthly. How do you find them. Go to www.kernscheduling.com
You can become a new shopper for them today. By signing up with them you will have access to shops from over 60 different companies.
PO Box 14094
Tucson, AZ 85732-4094
New shoppers can register at http://kernscheduling.com/shoppers/code.php
I recommend allowing email notification for shops. You will start receiving emails with available shops. They have a job board that is updated on a regular basis.