For some reason I couldn’t easily find how to enable the compose-key in Gnome 3.4. All the references I’ve found did not match the actual menus and dialogs that I saw on my system. That is including the official GNOME help pages. So I’ve 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.