I have a tool which I have written in python and generally should be run as a daemon. What are the best practices for packaging this tool for distribution, particularly how should settings files and the daemon executable/script be handled?
Relatedly are there any common tools for setting up the daemon for running on boot as appropriate for the given platform (i.e. init scripts on linux, services on windows, launchd on os x)?
To answer one part of your question, there are no tools I know of that will do daemon setup portably even across Linux systems let alone Windows or Mac OS X.
Most Linux distributions seem to be using start-stop-daemon within init scripts now, but you're still going to have minor difference in filesystem layout and big differences in packaging. Using autotools/configure, or distutils/easy_install if your project is all Python, will go a long way to making it easier to build packages for different Linux/BSD distributions.
Windows is a whole different game and will require Mark Hammond's win32 extensions and maybe Tim Golden's WMI extensions.
I don't know Launchd except that "none of the above" are relevant.
For tips on daemonizing Python scripts, I would look to Python apps that are actually doing it in the real world, for example inside Twisted.