Having trouble installing the ADB drivers for your Google/LG Nexus 4?
After much trial and error, I found a solution that worked for me, as of 08 May 2013 with Jelly Bean 4.2.2.
First, use the Nexus 4 Toolkit to install the ADB driver. It also comes with tools to root and backup your phone if you so desire.
Alternatively, if you only want to install the driver, you can go directly to Koush's universal ADB driver, which the Nexus 4 Toolkit uses.
I had trouble trying to install the default Google ADB drivers that came with the Android SDK. For some reason, I guess the driver is not signed and the 64-bit version of Win7 refuses to install unsigned drivers. Oh well.
Next, make sure your ANDROID_SDK_HOME environmental variable is set correctly. I had installed an earlier version of the Android SDK, so mine was pointing to the wrong location.
It should point to where your .android directory is located - usually c:\Users\[YOUR_USERNAME]\.android
Set the environmental variable by right-clicking on "Computer" and selecting properties > Advanced System Settings > Environmental Variables.
You may also want to add the platform-tools directory to your PATH so that you can run ADB from any location in your command prompt.
Next, restart the ADB server by typing "adb kill-server" followed by "adb start-server".
On your device, you should have the Developer options > USB debugging turned on. If you don't have the Developer options enabled, you can do so by going to Settings > About phone and then tapping on Build number seven times.
If all goes well, you should see a pop-up on your Nexus 4 asking you if you want to accept connections from your computer. This is a new security feature in Jelly Bean 4.2.2 and you'll have to accept the device fingerprint if you want adb to work.
There you go! Have fun with your adb-enabled Android device!