You should make sure your device is charged over 50% and WI-Fi is recommended to make the download as fast and painless as possible. As with any other OTA, you might not receive it right away. These thing take time to hit all devices. You can manually check in the Settings> Phone Info > Software Updates then tap the check now button.
Now that the official build is out, we should see a little more ICS development take off for both devices as well as various models around the globe. Now if we can just get the update to make its way to the states we would all be a lot happier. That might take a while though.
Source: HTCinside