There are two very extensive guides for the RPM and Dpkg package formats that will give you and introduction.
The RPM-Guide by Eric Foster-Johnson and the Debian New Maintainers' Guide. We will not try to duplicate them but concentrate on the openSUSE tools and workflows which means all our documentation expects that you know your way around the package formats.
All packaging happens in the openSUSE Open Build Service instance, our open and complete distribution development platform. Therefore the most important piece of documentation for you as a packager is the Build Service Tutorial. Its very RPM centric so we have another document describing Debian builds. You can also have a look at the Tips and Tricks and, if you are interested to build for more than one distribution, at the Cross Distribution Howto. The process of publishing fixed packages for already released products is covered in the Maintenance Portal.