You have to apply to become a mystery shopper just like any other job. There are businesses that hire mystery shoppers directly and ones that hire a mystery shopping company to do all the dirty work for them (the mystery shopping company uses their own independent contractors that report the shop and then they turn around and take that information to their client).
I am going to focus on getting a job with an mystery shopping company. They will send you a variety of shops and you will be able to choose which ones work for you. The main company I work for sends everything from fast food, electronics, and grocery stores, to tax and cell phone shops. It is a great way to get experience if you want to try to work solely with one main company in the future and it is also more flexible (if you work with one store then it will be more of a part time job – you will be in charge of a specific geographic area).
The first step is to get hired! You will need to apply and the applications look very similar to regular employment forms. Make sure that you are observant of time! Have a second hand watch or a timing cell phone with you at all times. There will be tests on many of the applications to try to gauge how observant and detailed you are.
These companies hire you as an “Independent Contractor”. This means that they will not send 
you a W2. If you earn more than $600 then they will send you a 1099. Keep track of your own earnings and expenses for tax time.
Here are some of the best companies to apply with. Don’t get discouraged! I applied with quite a few different companies and I really only use one main one. Try them all and see which ones work for you.
Best Mark
Certified Reports
Cyber Shoppers Online
Second to None
Market Force
Mystery Guest
There are lots more, but these ones are some of the best. If you have other companies that you have had great experiences with then please email me or leave a comment and I’ll add them to the list!
{ 2 comments… read them below or add one }
Great info!
Do you recommend applying to more than one place at at time? If more than one accepts you, then you can still pick and choose assignments from all of them, right?
Also, given your experience, do you think it’s worth the time? How much time would you say it takes to do one shop?
I definitely recommend applying to more than one. That way you can pick and choose which ones you actually do 🙂
I think it is worth the time. It will tell you approximately how long it will take and your payment so you will be able to decide yourself.
I am willing to do a grocery or restaurant shop for less because those are things I like to do anyway. Retail stores usually take about 30 minutes and I end up with some free stuff and a small payment so it depends on my mood.