So, you’ve heard about jailbreaking, and it sounds intriguing. And dangerous. (But mostly just intriguing.) Here’s how to hack your iPhone, iPod Touch or iPad—yes, iPad—into an unrestricted, freshly empowered mega-machine.

Jailbreaking: The What and the Why

In buying an iProduct, you’re accepting that its fate will be dictated by Apple. They control what kind of apps you install on your device, which of the hardware functions you can exploit to their full potential, and which carrier you can use your iPhone with. They’ve loosened up on at least one of those fronts in the last year or so, expanding the types of apps available in the App Store, but many—screw that, most—of the same restrictions still apply. Want to install an app that Apple hasn’t explicitly approved? Sorry. Want to use an app over 3G that’s been designated for Wi-Fi? Nope. Want to tether your phone? Run applications in the background? Change your device theme? Install system-wide gestures? No. Such. Luck.
Enter jailbreaking. In technical terms, to jailbreak is to enable a device to run code, meaning programs or system modifications, that hasn’t been sanctioned by Apple. Its roots reach back to a time when there were no apps for iPhone OS, and a clever group of hackers zeroed in on some exploits gave people their first way to install apps on their devices, by way of an underground App Store called Installer. It used to be that you could hack your device simply by visiting a webpage. That was two years ago. Since then, the iPhone and iPod Touch have been given a legit App Store, Apple has closed one security hole after another, and jailbreaking has become alternately more and less difficult, depending which device and software version you have.

Supported Devices & Firmwares
All firmwares (upto iOS 5)

• iPod touch 3G
• iPod touch 4G
• iPad 1
• iPhone3GS
• iPhone4 (GSM)
• iPhone4 (CDMA)

Now, lets get started…

Procedure
Step 1: Download the new Redsn0w 0.9.9b7 from below.
Download for Windows :

Download for Mac :

Step 2: In order to just jailbreak your iOS device, simply click on “Jailbreak” button and follow the standard onscreen instructions to enter DFU mode in order to install Cydia on your device.
If you are not using any Beta firmware (like iOS 5), Redsn0w 0.9.9 will automatically fetch all the important bits from the required firmware files without bothering you to download those large IPSW files.
If you are using iOS 5 Beta firmware, you will need to provide the .IPSW firmware file manually.
Step 3: That’s it! You are done with the jailbreak. Optionally, you can use extra features found under “Extras” option. This includes options such as entering DFU mode, booting in tethered mode (required by all tethered jailbreaks: iOS 4.3.5, 4.3.4, iOS 5), fetching, verifying or using SHSH blobs, changing boot logos and more.
WARNING !! iOS 4.3.5 & 5 users don’t turn off/reboot your phone after jailbreaking.
Unfortunately for iOS 4.3.5 & 5 users have to go through tethered mode everytime  they wish to reboot their idevices. Don’t worry, it’s actually nothing. To enter tethered boot mode, connect your idevice to PC and go to Extras option in Redsn0w. You’ll find tethered boot there.

FAQ

What are the Downsides?
As mentioned before, there is a real risk of bricking your device, or losing data. But beyond that, there are stability issues with some jailbreak apps, and using apps like Backgrounder can seriously diminish your battery life. Also, flaunting your new found ability to tether your phone by running, say, torrents through your 3G connection is a good way to get in trouble with your carrier.
What about future software upgrades?
Apple’s software updates almost always break jailbreak. When they come out, hold off on upgrading until the jailbreak community develops a hack, or an upgrade path. Upgrading to new software versions after a jailbreak often means installing a patched version of the update, specifically for jailbreakers.
Why did I click that “Make My Life Easier” button?
If Apple does thwart jailbreak in its next software update (likely), and you accidentally upgrade, you could be locked out of jailbreaking forever. Seriously! Why? Because as of late, Apple has been cracking down on jailbreakers by forcing their devices to authenticate with official servers every time they’re upgraded or downgraded.
What this prevents, specifically, is restoring to older versions of the iPhone/iPad software, which contain the security holes necessary for jailbreaking. By keeping users from downgrading, Apple essentially locks them out of jailbreaking once they’ve upgraded to an un-jailbreakable OS.
The button you pressed in Cydia remotely saves what’s called an SHSH blob, which is the “Go!” signal passed from Apple’s servers to your specific device. In the event of a later downgrade, iTunes can be spoofed into thinking that Apple has approving the device’s software change, when in fact it’s just the Cydia store’s servers giving the green light. The downgrade process is something we won’t have to worry about until Apple issues another update, after which I’ll update this guide. Until then, you can get a rough idea of how this whole thing by reading Saurik’s (the guy behind Cydia) blog post on how it works.
Will It Work With OS 5.0?
Surprisingly, yes! OS 5.0 builds seem to respond well to jailbreaking with the Redsn0w tool.