Some methods: 1. Change your layout from "USA" to "USA International (AltGr dead keys)". Then use right-alt+key to make various special characters (you can lo

Some methods: 1. Change your layout from "USA" to "USA International (AltGr dead keys)". Then use right-alt+key to make various special characters (you can look at what each character does at "Show Current Layout"). 2. Enable the "compose key" -- I use the Menu key for this -- which is described at http://sivers.org/compose-key http://sivers.org/compose-key (it's simple to enable: Keyboard Preferences→Layouts→Options→Compose Key Position). Both of these are customizable, so you can add your own combinations if you want. There are some other ways: 3. Ctrl-Shift-U in a GTK+ text input to enter a code point, as you said. 4. Alternative input methods that let you type special characters in in various other ways, such as LaTeX names, if you prefer that.