Before beginning, make sure you have git installed by running the following command in the terminal:
sudo apt-get install git-core
Proceed with compiling Gnome Shell Extensions:
git clone http://git.gnome.org/browse/gnome-shell-extensions
./autogen.sh –prefix=/usr –enable-extensions=user-theme
make && sudo make install
If you get errors, like I did, with the following commands above, you can download and install this .deb from here instead.
Now that Gnome Shell extensions have been compiled or the user theme deb was installed, it is now time to install the ThemeSelector extension.
Download the Themeselector Gnome Shell extension here. Extract it and place the “extension.js” and “metadata.json” files in the ~/.firstname.lastname@example.org/ folder (if the folder doesn’t exist, create it). Next, copy all the other theme folders you extracted to the ~/.themes/ folder. (it’s a hidden folder in your home directory, press Ctrl + H to make it visible; if some of those folders exists, merge the data).
Finally restart Gnome Shell by pressing Alt + F2 and running r.
>Gnome Shell themes to choose from are in the Activities menu under Themes.
Tip: Check out my post here on how to add more themes to the extension.