[GUIDE] How To Jailbreak 4.1 iPhone 3GS/4,iPod Touch 3G/4G with limera1n
Download the limera1n from here
Double click the limera1n icon to run it, and press make it ra1n.
You will now be told your phone is being put in recovery mode.
iTunes may at this time pop up and say it's detected an iPhone in recovery mode – don't click OK, just press the X in the top right to close the alert popup.
limera1n will tell you to press home and power at the same time, go ahead and do so. At one point, it will then tell you to let go of power (the top button on your device). Shortly after that limera1n will tell you you're in DFU mode – it's now safe to let go of the Home button as well.
Now you sit tight a minutes or so, and you'll then get a message letting you know you're jailbroken! Let's go ahead and continue to install Cydia on your device though.
You'll see a limera1n icon on your iDevice now (it may be all white unless you've restarted your device). Tap it to open limera1n, and tap Cydia, then Install on the top right. It will show it's Downloading Cydia…
The device will restart, and Cydia should show up now. I had to restart the phone twice in order for it to show up, but it's there.
Tap Cydia to open it, and you're all set!
It will do it's initial reorganization and then close, and NOW you're jailbroken and ready to enjoy it. :D