My phone is: Samsung Galaxy Nexus

My current Android version: 4.0.4 , IMM76I

I successfully installed andorid version 4.1 on my phone as below:

0) Download and Transfer file (bigxie_maguro_OTA_JRO03C-signed.zip = about 238 mb via his page: http://forum.xda-developers.com/showthread.php?t=1737849 ) to a folder in your SD card
1) Download and install and Use Samsung Galaxy Nexus Toolkit v 7.4 (this is a program which should be installed in your computer)
2) Power off your phone.
3) Power+Vol Down+Vol up.
4) Run item 6 on Toolkit (flash recovery): CWM
5) Run CWM
6) Go to your phone and choose Recovery Mode
7) Wipe all Data
8) Wipe all Cache
9) Install file from SD card (bigxie_maguro_OTA_JRO03C-signed).
Finish.

Enjoy it!

extra link:

http://www.redmondpie.com/download-and-install-android-4.1-jelly-bean-on-galaxy-nexus-gsm-how-to-tutorial/