Using GNOME/Character palette
Character Palette is an applet that displays a set of special characters in the panel, to allow characters which are missing from the currently configured keyboard to be inserted wherever text may be typed.
To insert a character, click on the desired character in the panel. This will copy the character into the clipboard. It may then be pasted into the text being typed (by CTRL-V, or the middle mouse button, for example).
To change the characters available for insertion, click on the caret (^) — or caron (v), if the applet is on the upper panel — at the start of the list and pick another palette of characters from those displayed.
To configure the applet, right-click on that part of the panel, and select Properties. This will allow new palettes of characters to be added, and existing palettes to be edited or removed. There is no special method for entering characters into these palettes; you will have to paste them from somewhere, or know the keyboard shortcut for the relevant Unicode or ASCII character.
As of version 2.14.3, there is no mechanism to change the order in which the palettes of characters are shown in the pull-down list. The configuration file, called %gconf.xml, is stored in ~/.gconf/apps/panel/applets/applet_X/prefs, where X is the index of the applet. Since GNOME will randomly place the file of interest in any of several subfolders, to find the file, search the ~/.gconf/apps/panel/applets path for a %gconf.xml file containing the string "GNOME_CharpickerApplet". The XML configuration file for the Character Palette applet will be found in the subfolder named "prefs". The file can be edited with a text editor to move character palettes up or down the list. Each entry is contained within XML list tags (<li> </li>). Initially, the file will not be populated with the complete list of palette entries, until at least one entry is edited through the Properties dialog, as described above. After moving the palette entry and saving the XML file, it is necessary to exit and restart one's GNOME session, or restart the machine before the change becomes visible in the Character Palette pop-up list.
If the Character Palette applet is removed from the panel, upon re-installation on the panel it will be reset to the default palettes and previous customizations will be lost. It is also likely that the configuration file will appear in a different path under .../applets/.