It's all in debian-kit-en.html, but just in case:
1) End running kit with "deb u" or "deb k"
2) Download newest debian-kit*.shar
3) Unpack with "sh /sdcard/Download/debi*.shar"
Confirm with "Y" (preserves IMG= setting)
4) Run "/data/local/deb/mk-debian -u"
And just in case you changed your ROM version lately:
Run "deb c" to clean any old symlinks from the debian
file system.
Sven-Ola, as of Feb-2013