Those are some of my custom settings for Gnome 3 on Ubuntu 12.04

With a standard user :

gsettings set org.gnome.desktop.media-handling autorun-never true

gsettings set org.gnome.shell.calendar show-weekdate true

# Depending on the gnome shell version :
gsettings set org.gnome.desktop.interface clock-show-date true
gsettings set org.gnome.shell.clock show-date true

gsettings set org.gnome.SessionManager logout-prompt 'false'

gsettings set org.gnome.nautilus.preferences always-use-location-entry true

gsettings set org.gnome.desktop.interface menus-have-icons true

gsettings set org.gnome.desktop.interface buttons-have-icons true

gsettings set org.gnome.desktop.background show-desktop-icons false

gsettings set org.gnome.nautilus.desktop network-icon-visible false

gsettings set org.gnome.nautilus.desktop home-icon-visible false

gsettings set org.gnome.nautilus.desktop computer-icon-visible false

gsettings set org.gnome.nautilus.desktop trash-icon-visible false

gsettings set org.gnome.nautilus.desktop volumes-visible false

gsettings set org.gnome.nautilus.preferences enable-delete true

# or :

gsettings set org.gnome.nautilus.preferences show-delete-permanently true
# Cf gsettings list-recursively | grep nautilus

gsettings set org.gnome.nautilus.preferences default-folder-viewer 'list-view'

gsettings set org.gnome.nautilus.icon-view default-zoom-level small

gsettings set org.gnome.desktop.wm.preferences audible-bell false

gsettings set org.gnome.desktop.wm.preferences visual-bell true

gsettings set org.gnome.desktop.wm.preferences visual-bell-type frame-flash

# Highlight the mouse cursor when you press Ctrl
gsettings reset org.gnome.desktop.interface locate-pointer

# Change the max screencast duration
gsettings set org.gnome.settings-daemon.plugins.media-keys max-screencast-length 600

# Old key :
GSETTINGS_BACKEND=dconf gsettings set org.gnome.shell.overrides button-layout ":minimize,maximize,close"

# New key :
gsettings set org.gnome.desktop.wm.preferences button-layout 'appmenu:minimize,maximize,close'

dconf read /org/gnome/shell/enabled-extensions # you can write also...

Additional tags : gnome3, tweak