A while ago I put together a cheat sheet with all of the most common voice commands. I printed it out and kept it in the car just in case I forget something. The whole point was, to have the info handy so that eventually I'd memorize all of the commands and wouldn't need to refer to it. It worked, so I thought I'd share it with everyone. This is especially helpful to those who have just acquired their vehicles.
Most of this is from page 94 of the Navigation Manual. It's a lot easier having this on one sheet of paper then it is thumbing through a manual while driving.
If you'd like to speed up the voice recognition process, a good way to do it is to turn off "Speech Confirmation Feedback". Go to the Configuration Menu/Navigation/Voice Prompt/Speech Confirmation Feedback. Uncheck this. Now, when you give a voice command, instead of hearing the lady repeat the entire command, you'll just hear a beep to confirm that the command was received. Much quicker!