Enter toned pinyin with Mac OS X

Enter toned pinyin with Mac OS X
Activate the "US Extended" keyboard in System Preferences (under "International" -> "Input Menu" ) and then do:
alt+a and then <vowel> to create the first tones: ā, ī, ē, ō, ū
alt+e and then <vowel> to create the second tones: á, é, í, ó, ú
alt+v and then <vowel> to create the third tone: ǎ, ǐ, ě, ǒ, ǔ
alt+` and then <vowel> to create the fourth tone: à, ì, è, ò, ù
u and then shift+alt+u and then shift+alt+<a, e, v or `> gives ǖ, ǘ, ǚ or ǜ.

(From Wikipedia)