How to file a bug report on the Debian installer (for Debian developers)

It seems that very few people who are not Debian installer developers can work out which package to file a bug report on for installation. Since this is gotten wrong so often, and always ends up wasting the time of one or more developers to categorise the bug report, I hope at least Debian developers and more experienced users can take the time to read the guidelines below before filing bug reports.

Please do use the d-i tag for bug reports, if the bug has to do with the debian installer or at least affects standard Debian installs.
d-i is not the old boot-floppies installer. Please do not file a bug on boot-floppies unless you installed a distribution prior to sarge.
Do not file bug reports on the install or installation pesudo-packages. We would like these pseudo-packages to be removed but have not convinced the BTS admins to do so. In the meantime your bug will likely rot there until one of the (infreqeunt) triages of these pseudo-packages.
If you have a general report about an installation, with multiple problems, and/or you can't be bothered to figure out what the right package is, then file an installation report, against the installation-reports pseudo-package, using the template, and filling it out completly. Note that incomplete templates may be be ignored. Given the time it takes to fill it out correctly, your time may actually be better spent in reading on and figuring out the proper place to file the bug. And only a few overworked people read and process these, so we tend to use them mostly to spot frequently reported issues. While your report will probably be skimmed quickly by a couple of people, there are about 900 before it in the queue for more detailed processing. If you would like to help, see here.
If you would just like to report a success, perhaps with general comments, feel free to file an installation report. We love these, and will be happy to close it immediatly while incrementing our internal it_seems_to_work counters.
If the bug is a kernel bug, then file the bug report on the apropriate kernel package. Filing bugs on the kernel pseudo-package is a valid choice, but will probably lead to a less effective response than filing it on the actual problimatic kernel source package. d-i uses the same kernels that are in the Debian archive as debs, so this applies even to kernel bugs that break the installer.
If the problem occurs during base system installation, you should be able to read the logs and work out what deb is breaking debootstrap and file a bug on it or on debootstrap.
If you've gotten to here, I hope you can take the time to work out the appropriate udeb on which to file your bug. I expect you'd have no difficulty with working out the buggy deb if the problem occurred as part of the second stage of installation -- after the base installation and reboot into the new Debian system.
You generally don't file a bug on general; instead you track the error message or other problem back to a specific package and file the bug there. Well, the same applies if the problem ocurred as part of the first stage of installation. Unless the problem is specific to the installer's initrd or other media, or is too general to fit anywhere else, debian-installer is generally the wrong place to file the bug, and bugs incorrectly filed there have to occasionally be triaged to the right packages.
If the bug is some other problem in the installer itself, then look at the logs, which are marked with the names of the udebs. Or run the installer in expert mode to get a good idea of which menu item (== udeb) causes the problem. It might help to familiarise yourself with the set of udebs that make up the installer, perhaps by looking though the d-i Packages file. In general the names are quite obvious; things like choose-mirror, base-installer, grub-installer and partman (for partitioning). If you have a debconf message and want to trace it back to the udeb that contains that message, check out the pot file for the entire installer. If you have a file on the d-i initrd that you have determined is at fault, you'll have to use some guesswork or look through our svn archive, since there is no Contents file for the installer (yet).

It might take a few minutes to learn which udeb to file a bug report on, but by doing so you save the d-i developer's time and begin to learn about what components make up the installer. For a Debian developer, it's not far from here to making contributions and bugfixes of your own..