[Fedora-join] RPM Packaging learning resources

Hello, in the future I would like to become package maintainer and help maintain some packages in Fedora. In the meanwhile I would like to learn more about RPM packaging format, related tools and probably experiment with COPR on some packages I would like to maintain.  What are some helpful resources/manuals to understand the RPM packaging process, the tooling involved, best practices and how the COPR works? Thanks in advance