Don't forget to unlock your N4 before you get too comfy! (howto)

If you plan on flashing any sort of update manually in the future (who knows, maybe during I/O 2013), then you should probably unlock your phone's bootloader now. Why now? When you unlock your bootloader, you lose all of the data on the phone so it only makes sense to do this before you have become too far acquainted with it and have all of your settings done your way.

NOTE: Unlocking your phone's bootloader will have no ill effects on your user experience, NOR will it affect receiving OTA updates at any point. As mentioned in one of the replies, it is true that this will leave your device rather vulnerable to anybody with fastboot experience. (ie) if you lose your phone, the data is accessible via command prompt whereas before, it wouldn't have been.

So how is this achieved? There are a few tools on the market, but I think it's nice if we do things the old-school way.

  1. Download the Android SDK. This is an archive - you'll need the drivers found in here as well as the adb and fastboot files for later. Just extract it in an easy-to-get-to location.
  2. Put your phone into PTP usb mode. That is, plug it into the computer and when the USB computer connection shows up in your notification drawer, tap it to go to the settings, then choose PTP (as opposed to MTP).
  3. Enable Developer Options. In Android 4.2, these options are hidden. To make them show up, go to settings, about phone, and then to to the bottom where it states your "Build Number". Tap on this field repeatedly until it says you're a developer (~7 times). Now your developer options are in your settings.
  4. Enable USB debugging. You'll find this option in the developer options. Once done, you should see a jelly bean in the notification drawer.
  5. Install the ADB driver. Plug your phone into your computer [again]. Chances are you don't have the driver installed for it yet in ADB mode. Go to your devices (device manager or just devices & printers) and find the phone. Right click the device, go to hardware, then properties, then to to driver (in some cases, change settings, then driver). Now click update driver. Search for the driver on your computer, in this directory: adt-bundle-windows\adt-bundle-windows\sdk\extras\google\usb_driver (the first folder here is the extracted SDK main directory). You'll have to fill in the first bit on your own. After this is done, the driver should be installed. If not, then, well, post, and I'll try to help you out. :P
  6. Open the command prompt (win+r >> cmd). Now type in the drive letter of your SDK directory. For me, it was 'E:'. Now change the directory to the folder where the ADB file is. For me, I did this by typing in: 'cd Downloads\adt-bundle-windows\adt-bundle-windows\sdk\platform-tools'. You should be able to change this to suit your purposes.
  7. With the phone plugged in and USB debugging enabled, type in 'adb devices' into the command prompt and look for your device to be listed. If it is listed, carry on, you're doing a great job!
  8. Now type in 'adb reboot-bootloader'. This will automatically restart your phone into the bootloader/fastboot mode which will allow you to unlock it. You should see and android and some text on the screen with options on the top (Start/Reboot/Recovery/etc). Ignore the options, time to hit the command prompt again.
  9. Our final bit of command prompt wizardry is this: 'fastboot oem unlock'. Notice how we're using fastboot commands now instead of ADB commands? It's because now we're in fastboot mode instead of ADB (USB debugging) mode. If nothing happens, double check to see if the driver exists for the device in this mode.
  10. Your phone should now reboot with a little open padlock at the bottom of the screen. Congrats, you did a wonderful job! Now you can flash updates and files without having to worry about wiping your phone in the future. :)

Let me know if you have any questions. Have a good day!