Today is the day I planned to upgrade JellyBean (Android OS 4.1) on my Galaxy Nexus. Here are the steps I followed.
1. First you will need to root your phone and install ClockWork Mod. I followed this great guide – http://bit.ly/MKlHPU
2. Next you will need to boot your phone, run the Super User app and accept the terms and conditions
3. Install BusyBox by downloading it from the market
4. Open BusyBox and accept the terms and conditions and click Install
5. Next, I followed this guide to install the OS – http://bit.ly/Pgiw4v
6. Enjoy!