Do this in case you installed Kubuntu before and want to have gnome available as well
sudo aptitude update
sudo aptitude install ubuntu-desktop
KDM or GDM as default display manager:
The default can always be changed later by modifying the /etc/X11/default-display-manager file. For KDM, the file should read /usr/bin/kdm; for GDM, the file should read /usr/sbin/gdm or /usr/lib/kde4/bin/kdm for KDE 4
install simple compiz configuration dialog
sudo aptitude install simple-ccsm
then you can configure compiz using:
install emerald window manager
sudo aptitude install emerald
Then register emerald under System → Preferences → Sessions → Startup with name: Emerald Fix and command: emerald -replace.