UPDATE: Due to changes in the public release of iTunes 8.2, you will now need to quit iTunes and run a command in your Terminal before proceeding with the instructions below. The command is: “defaults write com.apple.iTunes carrier-testing -bool TRUE”.

UPDATE: I’ve downloaded the Telstra and Vodafone bundles and made similar modifications, so they’re now available in the guide. If you’re using Telstra/Vodafone and my modified settings bundles work, please let me know in the comments as I’m unable to test it myself.

The following instructions are intended for members of the Apple Developer Connection (ADC), running an iPhone with a developer version of the iPhone OS 3.0 software. This guide also only provides Australian carrier settings for Telstra, Vodafone and Optus (plus resellers like Virgin), but if you follow the link to Crunchgear in the first step there are instructions on downloading and modifying the carrier setting bundles.

1. Download Telstra_au.ipcc, Vodafone_au.ipcc or Optus_au.ipcc, which were created as per the AT&T instructions on Crunchgear (note that the file should have an “.ipcc” extension, not “.zip”. If your downloaded file has a “.zip” extension, unzip it to produce a “Carrier_au.ipcc” file)
2. Open iTunes
3. Plug in your iPhone
4. Select you iPhone under devices
5. In the Summary tab, ⌥-click (option-click) the “Check for Update” button
6. Select the previously downloaded Telstra_au.ipcc, Vodafone_au.ipcc or Optus_au.ipcc file and click “Open”
7. Once the settings have been copied, disconnect your iPhone
8. Restart your iPhone
9. Open the Settings application on your iPhone, and navigate to General, then Network, and finally Internet Tethering
10. Turn Internet Tethering on. At this point, tethering is now possible via USB when your iPhone is plugged in. If you’d like to use Bluetooth, continue reading
11. You will be prompted to turn bluetooth on if it’s not on already. Select yes if prompted
12. On your laptop, turn on bluetooth and open the Bluetooth Preference pane
13. Click “Set Up New Device…”, which will open the Bluetooth Setup Assistant
14. Select “Mobile Phone” as the Device Type
15. Select your iPhone from the device list
16. A number should appear on your laptop, and your iPhone should prompt you for a pin
17. Enter the pin from your laptop into your iPhone
18. Once paired, make sure you keep “Use device as network port” selected
19. In the Bluetooth Preference Pane, make sure “Show Bluetooth status in the menu bar” is selected, since it makes things easier for starting and stopping tethering
20. Click the Bluetooth icon in your status bar, where you should now see your iPhone under devices
21. Click on the menu item for your device, and select “Connect to Network”
22. On your iPhone, you should now notice that the top of the screen has a blue bar titled “Internet Tethering”
23. You can now use the Internet!
24. As an optional extra, you can open Network Preferences and rename the two new network devices to “iPhone USB” and “iPhone Bluetooth”

Not really a difficult process, but it can be a bit fiddly. Downloading my preconfigured files also saves mucking around in Property List Editor, which most people will attest is a bit of a pain.