These are instructions on how to jailbreak your iPhone 3GS on the 3.0 firmware using RedSn0w for Mac. This tutorial can be used to jailbreak before applying the UltraSn0w unlock.

1) Create a folder on your desktop called Jailbreak

2) Download RedSn0w from here and place it in the Pwnage folder. Likewise, download the latest 3.0 firmware from below and place it in the same folder.
Firmware 3.0.0 (3GS)

3) Extract the redsn0w application from the RedSn0w zip file to the Jailbreak folder.

4) Connect your iPhone to the computer and launch iTunes.

5) Select your iPhone from the list of devices on the left. Now hold down Option and click the Restore button.

6) Navigate to the Jailbreak folder on your desktop and select the firmware ipsw. Click the Open button to continue.

7) Once iTunes has finished updating your iPhone to the desired firmware you may launch redsnw0w.app from the Jailbreak folder on your desktop.

8) Once RedSn0w opens click the Browse button

9) Select the firmware ipsw you placed in the Jailbreak folder on our desktop then click Open

10) Once the firmware has been verified click the Next button to continue.

11) Make sure Cydia is selected and click the Next button.

12) Plug your iPhone into the computer and make sure its OFF then click the Next button

13) RedSn0w will now guide you through the steps to get into DFU mode.

Hold down both the Home button and the Power button for 10 seconds.
Release the Power button and continue holding the Home button until RedSn0w detects the device.

14) Your iPhone will now reboot

15) RedSn0w will then begin uploading the new RAM Disk.

16) Once this is complete you will be notified that RedSn0w is done. Click the Finish button. When your iPhone finishes reboot (5 minutes or so). It will be jailbroken with Cydia on the SpringBoard.

Please refer to the firmware instructions, they both use the same method. This includes using the 3.0 firmware for this jailbreak.

1) Make a folder called "Jailbreak" on the desktop.

2) Download the following files and place them in the Jailbreak folder.

PwnageTool 3.1.4, found here
3.1.2 iPhone firmware (3GS): iPhone2,1_3.1.2_7D11_Restore.ipsw

When downloading the IPSW file, make sure your browser saves the file instead of tryin to extract it, firefox is recommened.

3) Double click PwnageTool 3.1.4 to mount it, then drag the PwnageTool icon into the Jailbreak folder.

4) From the Jailbreak folder double click to launch PwnageTool 3.1.4 and click Ok if presented with a warning.

5) Click to select Expert Mode from the top menu bar.

6) Click to select your iPhone 3GS, when selected a check-mark will appear over the image of the iPhone 3GS.

7) Click the blue arrow button to continue. You will be brought to the "Browse for IPSW" page. If PwnageTool doesn't automatically find the ipsw file you can click Browse for IPSW and manually select the 3.1 firmware you downloaded to the Jailbreak folder.

8) Click to select the found IPSW file, a checkmark will appear next to it. Then click the blue arrow button to continue.

9) You will then be brought to a menu with 7 choices. Click to select General then click the blue arrow button.

10) The General settings allows you to decide the partition size. Only check 'Activate the phone' if you are not with an official carrier then click the blue arrow button.

NOTE: Deselect Activate if you have an iPhone legitimately activated on an official carrier. Also you may need to increase the size of the root partition slightly. Your first attempt may fail at creating the IPSW until the size is increased to about 695 MB.

11) Next go to the Bootneuter settings, which should be greyed out for the 3GS iPhone. Click the blue arrow button.

12) The Cydia settings menu allows you to create custom packages so you do not have to manually install the necessary them later.

13) Click to select the Download packages tab. Then click the Refresh button to display all the available packages. Double clicking the package you want will download it and make it available in the Select Packages tab. Checkmark the ones you want then Click the blue arrow button.

14) The Custom Packages Settings menu displays listed package settings for your custom IPSW. For now leave these settings as is. Click the blue arrow button to continue.

15) The Custom Logos Settings menu allows you to add your own images as boot logos. Click the Browse button to select your Boot logo and Recovery logo. The rules for them: RGB or Grayscale format with Alpha channel and dimensions below 320x480. Click the blue arrow button to continue.

16) You are now ready to begin the pwnage process. Click the Build button to select it then click the Blue arrow button to begin.

17) You will be asked to save your custom .ipsw file. Save it to your Jailbreak folder you created on your Desktop. Your IPSW is now being built. Please allow up to 10 minutes. You will be asked to enter your administrator password. Do this then click the OK button.

18) You will be asked if your iPhone has been pwned before. If unsure click the NO button.

19) If your iPhone isn't already connected to the computer connect it now.

20) After delivering the payload PwnageTool will have placed your iPhone in recovery mode. Click OK to close the popup message telling you this. iTunes will also pop-up saying it has detected an iPhone in recovery mode.

21) In iTunes, hold the Alt/Option key and click Restore.

22) Navigate to the Jailbreak folder on your desktop using the dialog window that appears. Select the custom IPSW that was created (iPhone2,1_3.1.2_7D11_Custom_Restore.ipsw) and click the Open button.

23) iTunes will now restore the firmware on your iPhone. This can also take up to 10 minutes. Once done you will be rebooted into jailbroken iPhone OS 3.1.2!