Also the development version is available and in the AUR: AUR.
Once installed, you can start Guake from the terminal with:
After guake has started you can right click on the interface and select Preferences to change the hotkey to drop the terminal automatically, by default it is set to F12.
You may want Guake to load on starting up Desktop Environment. To do this, you need to
# cp /usr/share/applications/guake.desktop /etc/xdg/autostart/