How to Get tethering for iPhone 2G/3G/3Gs with 3.1.2 firmware
Did you know you can use your iPhone as a portable modem for your other devices? The first thing you need to do is set up Internet tethering on your phone. This is not difficult and requires only a jailbroken iPhone and a computer to do. Some hackers charge over $20 to tether your phone, and with this video, in a few simple steps you can accomplish it for free.
You Will Need:
*a jailbroken iPhone 2G, 3G or 3GS with activated Internet service
*a computer with internet access
Go to Blackra1n and select your operating system to download the software.
Plug your iPhone into yout computer via USB and click "make it rain". This will prepare your phone for unlocking (or jailbreaking).
Click OK and your device will then be unlocked.
Take you iPhone and open "BlackRa1n" to install "Cydia" or "Rock". Download these apps and their necessary upgrades and you have a tethered iPhone!