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 (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.
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 (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.