For some reason, I couldn’t easily find how to enable the Compose key in GNOME 3.4. None of the references I found matched the actual menus and dialogs that I saw on my system, including the official GNOME help pages. So I decided to document it here for my future reference.
- Go to System Settings->Keyboard Layout.
- Select the Layouts tab and click Options.
- Under Compose key position, select the key you want to use as the Compose key.
Wikipedia has a nice table summarizing the Compose key sequences.