How to install CyanogenMod 10 official nightly builds ROM Jelly Bean 4.1.2 on Samsung Galaxy S2 GT-I9100

Here is quick tutorial and steps of instruction on how to install  CyanogenMod 10 official nightly builds Custtom ROM Jelly Bean 4.1.2 (GT-I9100)

INSTRUCTIONS:
Users those are doing it for first time or coming from other ROMS

1. Make sure you're NOT RUNNING A KERNEL WITH THE MMC-SUPERBRICK-BUG. If you're unsure, flash this ClockworkMod-Recovery using Odin/Heimdall.
2. Go into Setting ->Developers option and enable USB Debugging on your Galaxy S2
3. Copy GApps and CM10 ZIPs to your internal SDCard
4. Boot into recovery using Volume up+power+home
5. Flash CM10 zip from SDcard
6. Flash Gapps zip From SDcard
7. Do factory reset
8. Reboot

Upgrading from pervious version of CyanogenMod

• Copy CM10.1 ZIP to your internal SD-Card
•  Boot into Recovery
• Flash CM10.1 zip from internal SD-Card
• Reboot

ClockWorkMod (CWM) Recovery Installation Instructions

• Go into Setting ->Developers option and enable USB Debugging on your Galaxy S2
• Power off your device
• Boot into Download-Mode using Volume Down + Home + Power
• Hit Volume Up to accept the warning
• Start Odin 
• Choose ClockworkMod-Recovery_abcd.tar as PDA
• Don’t mark re-partition
• Connect your Phone
• Start flashing

Download Links:

• CM10 nightly builds:here
• Gapps:here

NOTE: We have no responsibility to any damage to your phone

SOURCE