One tip I try to bring up often in storytime is the importance of repetition. In my baby storytime, for instance, we read two books, and one of those is the same every week. The babies and parents love it, they know what to expect, and it's a great way to bring up the importance of reading and re-reading beloved books.
But this also applies to toddler and preschool storytimes! I have favorite books that I use a lot, and whenever a child remembers them, it's a great time to slip in this tip: "Yes, we have read this story before. Isn't it great? Parents, repetition is an important part of learning. Your child may want to read their favorite books over and over again, and that's a great way to reinforce vocabulary and build a love of reading and stories. This book is one of my favorites, and some of you have read it with me before. Let's read it again together!"