Designed to assist with the creation of accessible content, EPUB 3 Accessibility Guidelines include a quality assurance checklist together with instructions on how to implement the requirements.
If you are new to accessible publishing, the best place to start is Accessible EPUB 3, published by O’Reilly. It will walk you through the issues you need to understand.
The EPUB 3 Best Practices book includes the information provided in Accessible EPUB 3 as a chapter.
You can download the EPUB 3 Accessibility Guidelines site as an EPUB Publication.
For general how-to questions, please create a new topic on the IDPF accessibility forum.