There are many details which have not been covered here, like how to distribute Unix daemons, configuration files and much more.

But most important, I want to emphasize again that for Debian maintainers, packages are source packages, not binary packages. They never interact directly with the internals binary packages. In fact only 'dpkg-deb' and 'dpkg' developers need to know what they are. In fact it is not recommended to do so.

If a developer were to explain someone how to build a Debian package, he will certainly explain how to make a source package and how to build it.

On the other hand, not every developer wants to submit his software to Debian (yet), but still wants to profit from the advantages a packaging system like 'dpkg' offers without releasing package source code. Personally I will release my freeware projects still as tar.gz files with source code etc. for all kind of platforms, while I plan to offer more and more '.deb' packages for the convenience of Debian users who just want to install and use my software.

If someone wants to do the next step to submit a software package to Debian, you have to move on to study the Debian New Maintainers' Guide as well as the Debian Policy Manual first. On your undertaking to create a Debian source package, also have a look at the debian-mentors mailing list to see experienced and beginning Debian developers interacting with each other and tackling similar problem you might encounter.