I am writing a short children's novel and I want to expand this into a series made of several short novels. I intend to write the whole series at once so that the internal universe is consistent and so that I can add an arc across the books. This arc though is not the focus of the story and I hope that readers will be able to pick up any of the books and start reading it without needing to read through them in order.

* What is a good technique for placing basic information about the characters and setting so that readers who started in the middle of the series are not lost and readers who started at the beginning do not feel bored seeing the same information again?
* Is there any series that has used this technique well?