How to backup guake's settings

Luckily you don't need to be an expert on dconf anymore:

guake --restore-preferences ~/myguakeprefs 
guake --save-preferences ~/myguakeprefs

UPDATE 2019

OUTDATED please check the new answer that includes --restore-preferences and --save-preferences

Backing up gconf /apps/guake and /schemas/apps/guake paths recursively.

gconftool-2 --dump /apps/guake > apps-guake.xml
gconftool-2 --dump /schemas/apps/guake > schemas-apps-guake.xml

gconftool-2 --load apps-guake.xml
gconftool-2 --load schemas-apps-guake.xml

Plus backing up directory ~/.gconf/apps/guake should do it.

More info here or issue 292 and issue 323