Enabling and Using US Extended on Mac OS 10.9
The US Extended keyboard gives you access to a much wider variety of diacritics, making it easier to type in a number of languages. This screencast will demonstrate how to enable the US Extended keyboard on Mac OS 10.9, and then use it to type Pinyin tones.
Note
If you are using a different version of Mac OS, please see my Foreign Language Software page to learn to enable different keyboards for those platforms.