Welcome to the forum!
Great job on your two first shops. The best advice I have is to read, read, and read. Pull up to your computer with a cup of coffee or another beverage of choice and give yourself some time, at least an hour or two at first, to go over the various threads, articles, and sections of this forum that were designed to help folks with questions just like yours.
Start in the "New Mystery Shoppers" section of the forum with the 'sticky' threads there. Those are the ones that stay at the top of the list. Then go to the Mystery Shopper Magazine portion that has a link at the bottom of every forum page and read a few articles at the link, "New Mystery Shoppers Start Here." If you want a diversion to see what is said about a particular company, go to the "Official List of Mystery Shopping Companies" also linked at the bottom of every forum page. There you will find discussions of more than 200 companies grouped by company. Peruse current discussions or post your own question or comment in the sections of the forum.
To do this as a business be prepared for a journey that is more of a marathon than a sprint. One last thing - Have fun with it.
Happily shopping Rhode Island and nearby Massachusetts and Connecticut