You sign up, are offered shops based on where you live, and you have to fill out forms and submit them for reimbursement. They can be for anything from a bank or windows, to a drugstore. My husband was even offered one for a tanning salon! Anyway, I am not an expert nor do I have all of the information compiled for you, but Carrie at Money Saving methods does! Her blog is phenomenal, and she has a ton of step by step information and even tells you the best mystery shopping companies, and gives you all the rules and "methods" for mystery shopping. I will tell you this: Do NOT EVER pay to be on a mystery shopping list!!! You should be able to register for free and then be offered shops. When you go to Carrie's homepage look at the left hand side bar, and she has a tab for Mystery shopping, click on it, and read the instructions thoroughly before signing up for any shops. Mystery shopping money has been one of the contributors to my monthly Snowflakes.
Now, while you are there, you need to check out the section for Online Offers. This could change your life! You know those pop up ads "Answer this question for a $500.00 Target Gift Card..."?
Well, some of them are real!!! I can speak from experience! I was able to get 2 $250 gas cards back in November by following Carrie's instructions. Now, again, read her instructions very carefully! She even has a list of legitimate offers you can choose from! She makes it so easy for you-and me! Carrie even answered an email I sent her asking for her help when I did my first offer. After I did mine, My Shop Without Money Sister did one, and we both received our gift cards. Let me tell you, there is no better feeling then not paying for gas from Thanksgiving until Valentine's Day!!!
Carrie lays out the best way to do this, to put out the least investment, and make the most profit. When I did mine I signed up for "offers" like Columbia House, Disney Movie Club, and different beauty products. For my free movies I picked gifts for my nieces and nephews for Christmas, and also the beauty products. I had half of my shopping done in September! All in all, it cost me about $75.00 to make $500.00.
Please read Carrie's instructions carefully, and feel free to ask questions, I will help the best I can! I have a home improvement project I am planning on doing, so I am going for a $500.00 Home Depot or Visa Card next! I hope this can be useful to you as well! Good Luck!