[Guide] How to unlock the Google Nexus S

The Google Nexus S bootloader has been unlocked. What that means is that you can now  access custom recovery mode on your device and install custom ROMs like the Cyanogen Mod etc.

For information on rooting your Nexus S check here

Continue reading or the the guide to unlock your Nexus S.

[NOTE] The process of unlocking the device may void your warranty. Please do not attempt unless you are experienced with the process and understand the risks of unlocking the bootloader

After checking both the links above you can proceed with your unlocking... Before you begin you will have to download the Android 2.3 SDK and Fastboot which you can download from here and install it on your computer.

1. Power Off your Nexus S completely
   
2. Hold Volume Up + Power button simultaneously.
• You should now be in Standard Recovery Mode.
  
3. Connect your device to your computer.
   
4. Open command prompt on your windows computer [Terminal if you are using a Mac] and type 'fastboot devices'.
   
5. If fastboot shows you as connected type: 'fastboot oem unlock'.
6. Select 'Accept' when prompted

That's it, your done... Your Nexus S is now unlocked and you can now install custom ROMs on it. While no ROMs are available for this device yet, stay tuned for some in the near future.

source - AndroidCentral