Say I am able to follow the packaging guides and have figured out how to make a working .deb and .rpm, how can I get distros to actually include my software?
What's firstly the quickest / easiest way, and secondly the most appropriate / official way?
What if my software depends on other people's libraries that do not have packages? Do I then get the responsibility of packaging those?
A couple of points based on my experience with Debian:
The devel is always in the details. I happen to be a Debian Developer and maintain some software for which I am the upstream author, but I also have other projects that I have not yet put into Debian and may not for some time as they are more specialised.