Then use the Phonetic First/Last Name fields. Once you fill them in properly, Siri won’t mispronounce your name or those of your friends and family.
To set a phonetic field in iOS 5, go to a contact’s entry from your iPhone, tap “Edit,” scroll to the bottom, and tap “Add Field.” Choose “Phonetic First Name” and/or “Phonetic Last Name” and fill them in.
To set a phonetic field in Mac OS X Lion’s Address Book, go to a contact’s entry, click “Edit,” In the “Card” menu, choose “Add Field” and “Phonetic First/Last Name.” When synced with iCloud, those phonetic names will appear on your iOS devices and iCloud-capable computers.
[Attribution: Shawn Blanc. Thanks to MacDailyNews Reader "Arline M." for the heads up.]