mark,
First, if you are not signed up with at least 75 of the companies on the list provided below, that may be part of the isse. By taking a coupe of jobs to try out many different MSCs, you will begin to find which job board's are worth watching for the sorts of jobs that you like. That said, some MSC's schedulers never contact individual shoppers, instead relying on broad anouncement emails or their job boards. Coveted jobs evaporate from the MSC job boards in minutes (seconds for some hotel jobs), so you need to have some experience to begin to see when an MSC is going to post new jobs each month/quarter.
When I started, I made it a point to sign up with 5-10 more companies on any weekday when I did not have a shop scheduled. That got me to a point, in about 4 months, when schedulers began to email or call me to offer jobs, and even some bonuses. By that time I was done 2 or more shops for at least 30 companies, so the schedulers were beginning to see a pattern of reliability. That, and high report scores, will bring offers. There are sooooo many unreliable shoppers, especially among newbies, that proving yourself early will bring big rewards in terms of offers.
Also, when you have a chance to, contact a scheduler with GOOD news. They get so much bad news that hearing about something good is a treat that will be remembered. (BTW, this works best with relatively small companies' schedulers, lol.)
Based in MD, near DC
Shopping from the Carolinas to New York
Have video cam; will travel
Poor customer service? Don't get mad; get video.