Introduction to German/Input

Windows
(for these characters ensure that the num lock is on)
 * For ä, hold down Alt, and press the numbers 1, 3, 2 on the keypad. Then release the Alt button.
 * For Ä, hold down Alt, and press the numbers 1, 4, 2 on the keypad. Then release the Alt button.
 * For ö, hold down Alt, and press the numbers 1, 4, 8 on the keypad. Then release the Alt button.
 * For Ö, hold down Alt, and press the numbers 1, 5, 3 on the keypad. Then release the Alt button.
 * For ü, hold down Alt, and press the numbers 1, 2, 9 on the keypad. Then release the Alt button.
 * For Ü, hold down Alt, and press the numbers 1, 5, 4 on the keypad. Then release the Alt button.
 * For ß, hold down Alt, and press the numbers 2, 2, 5 on the keypad. Then release the Alt button.

Alternatively you can use the US-International keyboard layout.
 * For ä, hold down AltGr, and press Q.
 * For Ä, hold down AltGr+Shift, and press Q.
 * For ö, hold down AltGr, and press P.
 * For Ö, hold down AltGr+Shift, and press P.
 * For ü, hold down AltGr, and press Y.
 * For Ü, hold down AltGr+Shift, and press Y.
 * For ß, hold down AltGr, and press s

Mac

 * For ü, ö, and ä, hold down option-u, release, and type u, o, or a.
 * For ß type option-s.

GNU / Linux
Set up a key on the keyboard as the compose key. In GNOME this can be found in via the System -> Preferences -> Keyboard utility, on the Layout Options tab. To type an a letter with an umlaut, press the compose key followed by " and then the desired letter. To type the letter ß, press the compose key followed by the s key twice.