Ask HN: Resources for learning RAG best practices?

What are some of the resources that will help me understand the best practices of AI agents using RAG? What are some of patterns and theory that one need to know? I'm open to: books, blogs, articles, papers, videos, literally anything. Thanks HN!

Answering an important question: “Why is it difficult to extract meaningful text from PDFs?” https://unstract.com/blog/pdf-hell-and-practical-rag-applica...