Attached is the QC Plot I made for a production of Charlotte's Web. Information includes what page the change occurs on (you can also add timestamps), who the actor is, where they exit before the change, where the change takes place, what they are changing out of, what they are changing into, where they enter after the change is complete, and what the change consists of. To make this form, you need a complete Entrance/Exit plot (or the blocking script), and a piece list from the costume designer.
I learned the basic format (modified since) working as an Intern at the Children's Theater Company in Minneapolis; this plot is not from a show done at that theatre.