How To Root, Unlock Bootloader And Flash ClockworkMod Recovery On Nexus 7

Part 1: Unlocking Bootloader
Step 1: Download and install Android SDK.
Step 2: Enable USB Debugging from Settings > Developer Options.
Step 3: Connect your Nexus 7 with PC via USB cable. Launch Terminal / Command Prompt, navigate to the fastboot folder which will be inside the location where Android SDK is installed (On Windows, it should be in C:\)
Step 4: Enter the following command:

fastboot oem unlock

Once flashing is complete, enter:

fastboot reboot

 Step 5: Download and place recovery.img [Goo.im] in the fastboot folder and type in the following:

fastboot flash recovery CWM-grouper-recovery.img

 Step 6: Reboot again by entering:

fastboot reboot

Part 2: “Making ClockworkMod Recovery Permanent”
Step 7: Now, in order to keep from losing access to ClockworkMod Recovery, enter the following commands in terminal:

mount system
adb shell
cd /system
mv recovery-from-boot.p recovery-from-boot.bak

Part 3: Gaining Root Access
Step 8: Download JB-SuperSU.zip [ClockworkMod] and place it directly under /sdcard on your device.
Step 9: Enter ClockworkMod Recovery by shutting off your device, pressing and holding Volume Up, Volume Down and Power buttons until you see the screen flash with the iconic CWM logo.
Step 10: From the main menu, navigate to install zip from sdcard > choose zip from sdcard > JB-SuperSU.zip
Step 11: From main menu, select reboot system now.
If you followed the steps correctly, your Nexus 7 tablet will now be rooted on Android 4.1 Jelly Bean. Go ahead and install your favorite root-only apps!
For queries, please visit the official thread over on RootzWiki.