I find the best way to proof read a piece of text (such as an email message) is by having my computer read back to me what I have written. I highlight the piece of text, right click->Speech->Start speaking.
Sometimes, I find that it doesn't pronounce words correctly. I found a built-in app (~\Applications\Utilities\VoiceOver Utility) Under speech, and the tab Pronunciation, where ostensibly I can tell the text-to-speech engine how to phonetically pronounce a word.
For some reason, the text-to-speech simply doesn't update, and continues to mispronounce words I have already entered into the dictionary. I've tried quitting my application, I've tried restarting my computer.. I just can't understand why it's not working. Help please!