I like to set up a specific day and time period for Mystery Readers such as Fridays afternoons. I write in the dates available on my sign-up form. (see below) It is easier on my planning! Next, I transfer the information from the sign-up form to my reminder slips. I clip these on to my lesson plan pages - ready to go when it is time.
I will schedule only one Mystery Reader per Friday. Here is a download of my Mystery Reader flyer and reminder slips:

A few of the amazing mystery readers from my classroom:



