Download sn0wbreeze 1.7: http://ih8sn0w.com/index.php/products/view/sn0wbreeze.snow
In this video I give a full tutorial on how to jailbreak your iPhone 3G, iPhone 3GS or iPod touch 2G on iOS 4 using sn0wbreeze 1.7 which was made by ih8sn0w. Before you begin there are a few things you will need:
iTunes 9.2
iOS 4 firmware for your iPhone 3G, iPhone 3GS or iPod touch 2G
An iPhone 3G, iPhone 3GS or iPod touch 2G on iPhone OS 3.1.2 that has been jailbroken by redsn0w, blackra1n or PwnageTool but NOT with Spirit. This is very important, otherwise you will not be able to use sn0wbreeze 1.7.
If you are running 3.1.2 or are able to downgrade your device back down to 3.1.2 then you should be able to do the jailbreak. If for whatever reason you can’t use sn0wbreeze don’t worry as there are two other jailbreaks coming soon that should be able to jailbreak you no problem. However if you have to be jailbroken on iOS 4.0 right now then you should be good with sn0wbreeze.