Good luck and welcome to the world of mystery shopping.
some tips that i find help me are;
use a word processor for your report comments
keep a log of your shops dates and times and milage to and from (this will help at tax time)
I use excell for a spread sheet, much easier to see who is paying me and when.
apply for as many jobs as you can do, also apply to as many companies as you can find.
Volition.com is a good source for companies.
once again, good luck and let us know how your first shop went.
Mike