It is fairly important to start your project with some means for communication. The most natural way to do this is with a mailing list.
Creating a new malinglist starts with a wishlist bug against lists.debian.org. This bug is in a particular format: [ FIXME: details for mailing list bug ]
Before your list can be created, the listmasters will want assurance that creation of the list is, in fact, necessary. So for this reason, don't wait for your list to be created. Start discussing your new project on email@example.com immediately. To help distinguish your project's posts from the large amount of traffic on this list, tag them in the Subject field with an agreed-upon tag, e.g. [desktop] for debian-desktop related threads. When sufficient discussion on the developer's list has taken place and it is time to move it to a subproject list, add to your wishlist bug report some URLs pointing to these discussions in the archives as justfication for creation of your list.
Again, getting a web page or two up to give people an idea as to what your subproject is about is fairly important to do. While there are a number of ways to go about this, the simplest is to put them on your developer home page at people.debian.org.
Another possibility, and one which is fairly attractive because it facilitates collaborative web site creation and maintenance, is to put a page on the Wiki at wiki.debian.net.
Finally, you'll want to give some thought to having a page created under www.debian.org/devel. While not as straightforward as maintaining a personal page or a Wiki site, this approach has its advantages. First, the site is mirrored everywhere. Second, the Debian web site translators translate pages into many different languages, reaching new potential audiences for your subproject and improving communication with subproject members and interested parties for whom English is not their most comfortable language. Third, a number of templates are available to make your site more integrated with the main web site, and to assist with incorporating some dynamic content into your site.
Work is under way to create a code repository system for Debian developers' own projects. [ FIXME: needs details ]
Once you have a list, or at least have done some preliminary discussion on debian-devel to determine you want to go ahead with your subproject, you are ready to make a formal announcement. Your announcement should include references to past discussions, any web pages and code you may already have, and summarize in a well-thought out manner what your project is setting out to achieve. Enlist the help of fellow developers on irc or in private email to look over your draft and work out the final wording before you send this out. Then post your announcement, signed with your gpg key, to debian-devel-announce and any other lists that may be relevant. You might consider some non-Debian lists as well, if that is appropriate.
Debian Subproject HOWTO12 February 2003