My trusty Nexus 7 tablet started running slow the last couple of months. Whether the cause is the dodgy electricity in South-East Asia, or my wife 
So I decided that, after 3 years of using vanilla Android on the Nexus, it was time to give it an overhaul and install cyanogenmod on my trusty sidekick. Here's a complete guide on how to install it from scratch!
Step 1: Prepare your pc & Nexus 7
Before we can actually install and debug the device, we need to setup a few things on the computer to make it accessible. This boils down to installing 'adb', 'fastboot', and the correct Windows drivers.
You could get all of these from the Android SDK, but that file is a whopping 3.5GB, and we only need a tiny fraction of it. Luckily there are plenty of Android developers out there. And one of them made this incredibly easy 15-second installer that installs only the components that we need.
Run it and say yes to everything. You now have access to the 'adb' and 'fastboot' commands through a command prompt!
Before we can connect our Nexus, we have to enable USB debugging on the tablet. Go to your settings. Scroll down to the 'system' part and choose 'About tablet'.
On the next screen, tap the 'Build number' 7 times, you'll see this:
Once you see the words 'You're a developer' appear on the bottom, hit back and you'll see the new settings option 'Developer options'. Enter that and enable 'USB debugging'.
Step 2: Unlock the bootloader
This is where the fun begins. Connect your Nexus to your computer and open a command prompt as administrator. Since we've used the 15-second installer, the commands are available system-wide. But before we go any further, a word of warning:
UNLOCKING YOUR BOOTLOADER WILL RESTORE FACTORY SETTINGS AND WIPE ALL THE DATA ON YOUR NEXUS!
So this is the ideal time to copy those cute baby-first-words videos to another hard drive! That counts for your porn collection as well...! Don't say I didn't warn you...
To check if your adb drivers are correctly installed, use the command 'adb devices'. You device serial number should show up. Let's reboot into the bootloader now and see if fastboot is working correctly. Use the command 'adb reboot bootloader'. This boots our nexus into the bootloader. Once that's done, use the command 'fastboot devices' from the command prompt. You should see your device's serial number here as well, as seen in this screenshot:
IF YOUR DEVICE IS NOT SHOWING UP, YOU MOST LIKELY HAVE A DRIVER ISSUE. CHECK OUT THIS GUIDE TO FIX THIS ISSUE!
Now that we are in fastboot mode, type the command 'fastboot oem unlock'
If all goes well, you'll get a confirmation window on your device:
This unlocks the bootloader and resets the phone to factory settings. Since the factory settings do not have USB debugging enabled, we'll have to go back to the end of step 1 and re-enable USB debugging. Go to Settings > System > About tablet and hit the 'build number' option 7 times. Then go into the developer options and re-enable USB debugging.
Step 3: Install custom recovery
Time to install a custom recovery which will allow us to install custom ROMs to our device. I prefer using TWRP, so head over to the TWRP download page and download the correct version for your device. There are 4 different Nexus 7 models, a 2012 model with wifi, another 2012 model but with 3g, then a 2013 version with wifi, and a 2013 version with LTE. Installing an incorrect one might result in a soft-brick, so make sure you pick the correct one.
Put the image file in the same directory as where you installed adb in step 1. Rename the file to twrp.img (to make it a bit easier) and reboot your device to the bootloader by using the command 'adb reboot bootloader'.
Once in the bootloader type the following command: 'fastboot flash recovery twrp.img'
Don't reboot your device just yet!
With your Nexus still in the bootloader, use the volume up and down keys to choose 'Recovery' on your device and use the power button to select it. You'll boot straight into TWRP recovery now.
Awesome! Your device is now ready to install custom images. You've just unlocked the full power of your phone and joined the cool kids club. Only a few more steps are needed to install Cyanogenmod and become the envy of your wannabe-hipster friends!
Step 4: Install Cyanogenmod
Grab the version of Cyanogenmod that you want at download.cyanogenmod.org.
Here's a quick explanation of the different builds they offer:
Nightly: usually generated every 24 hours, experimental, newest features, unstable
Experimental: testing version requested by device maintainers to evaluate specific changes
Snapshot: milestone snapshot, more stable than a nightly but potentially some issues
Release Candidate: last builds before stable release, few minor issues, mostly stable, and safe for daily use
Stable: most stable version available, all or nearly all issues resolved
I installed the nightly build because bleeding edge and experimental... You might want to take a snapshot or even stable version to make sure everything works as it should.
Download the file and copy it in the root directory of your device.
With your device still in TWRP, choose 'Install'. You should see the image file you just downloaded in the root of the sdcard. Tap the file and install the custom rom.
Congratulations! You just become the coolest cat on the block. You can now show off with an operating system used by less than 1% of the population. You are the epicenter of hipsterness!
On the other hand, the realization that there are no Google apps or services on your new piece of hipster electronics sets in right after first boot. You are left with no way to install any apps since the Google Play store is nowhere to be seen. On to the last step:
Step 5: Install Google Apps so you can use your nexus as a tablet again
Download the nano ARM version of GAPPS at the following link: opengapps.org
Put the file in the root directory of your device and repeat the steps from step 5. But this time install the gapps image you just downloaded. After it's installed reboot your device.
You now have a working Cyanogenmod tablet with Google services enabled. You can download any app again through the Google Play store! You can also revert to stock android by downloading the correct image and installing it through TWRP.
If you've got any questions or get stuck somewhere, let me know!
DISCLAIMER: This is a windows guide, if you use Linux, you don't need a guide to do this stuff. It should be very straightforward and you're probably a CLI monkey anyway! ;)
Follow me and subscribe to an eclectic mix of posts included, but not limited to futuristic rambling, surreal art, entrepreneurial hacks, personal stories, and some random awesomeness...