Theming Gnome 3, not counting theming Gnome Shell, is a huge pain. It is alot more complicated than it was with Gnome 2.x.UPDATE: You can install GTK themes easier using the Gnome Tweak Tool. Check out my post about it here.
To begin, place the theme you want to use in the /usr/share/themes/ folder.
Install Mutter (Titlebar) theme
To change the Gnome Shell Mutter (titlebar) theme you need to change the theme name in gconf. Press ALT + F2 and run:
Navigate to desktop > gnome> shell > windows. Double click the “theme” value and change it to the name of the theme you want to use:
Press ALT + F2 and run “r” to restart Gnome Shell, and apply the change.
Install Gtk3 Themes
To change the GTK theme in Gnome 3, you will need the Gnome Tweak Tool installed. If you do not have it already, check out my post here, or run the following command in your terminal:
sudo apt-get install gnome-tweak-tool
In the Gnome Tweak Tool, under Interface, select the Gtk theme to the theme you wish to use.
While you have the Gnome Tweak Tool open, you can change the icon and cursor themes if you like.