Collaboration between Ubuntu and Debian

I would like to cover how maintainers from both projects can coordinate over patches, bug, version control systems, roadmaps, etc. I am also going to include some lessons learned about what it's like to be a derivative distro of Debian, so I will use examples from the past where things went well (or didn't go well at all!) so that both Debian Developers and derivative's from Debian can learn what works and what doesn't.