Categories is typically introduced after a student has acquired over 200+ receptive and expressive labels.

When teaching categories, teach across operants. Teach sorting, receptive, expressive, and intraverbal.

Once students have mastered categories, move to fluency – how quickly can your student tact items within categories? Then do intraverbal level if you really want to exhaust categories.

Here is a great website for category flashcards: https://www.kids-pages.com/flashcards.htm

We also use these quite often: https://amzn.to/3nfdR6S