[Nexus 6 Q&A, Help & Troubleshooting] micmars:
I’ve split this into categories so that folks will have some basics right upfront.

1.First Use

1.1:You almost certainly will want to unlock your bootloader, inject root, recovery, etc.

I suggest reading the All-in-One Beginner’s Guide, where you’ll find everything you need to get started.

1.2. Learn Fastboot:

Yes, you have a Google device, and it is very easy to flash anything you want with a few simple command lines. Put bluntly, on Nexuses, the manual steps are very easy.

Hie yourself to this authoritative thread written by the prolific dev and highly respected forum member [MENTION=2872010]rootSU[/MENTION].

1.3:Toolkits: Toolkits are a fantastic way to do all of this from the jump. There's nothing wrong with toolkits themselves; they can be great, useful tools, but please learn to do the steps manually. Why? Simple. If anything goes wrong, and it can, knowledge of fastboot will save you; no knowledge of it, you're waiting on help from others, or learning from scratch that which you should already have learned. Further, should help arrive, that person helping you is bearing two burdens, helping you first learn the basics of command line, and solving your problem. That is downright unfair. OK, onto the toolkits. You can find them in the development sections, specifically:

Wugfresh's Toolkit for Windows Operating System

Nexus One-Click Mac Toolkit for the OSX

Skipsoft Unified Android Toolkit for Windows

1.4: Decrypt or Not Decrypt:

Please note: Decrypting your device will wipe your device, so if you are going to decrypt, please do so before taking all of your time to setup your device the way you like it.

IF you want to remain decrypted, put the zip file located in this thread on your device, throw it in your cloud storage (Dropbox, &c), keep it in your pocket, think well of that file.

IF you want to remain decrypted, that zip should be the LAST file you flash before any new rom or kernel is flashed, or if you are unsure if a rom has a kernel that will force encrypt your device.

There are differing opinions as to the wisdom of decrypting, and I don’t care whether you think it is better or worse; people want to do it.

You can learn more about it here, and can accomplish the task using the link previous link or using any one of the aforementioned toolkits.

1.5: Recovery:

You almost certainly want to make a backup of your device prior to tweaking, flashing an updated nightly, or testing a new rom. Recovery for our device can be found here.

You may want to put a nice theme on that TWRP, go here. Hint: The developer whom does those themes keeps up with each iteration of TWRP, and if a new version requires a new theme, check the theme thread before you update your recovery.

1.6: Starting Over

I believe that this community owes a special thanks to [MENTION=1567974]Q9Nap[/MENTION] and [MENTION=426561]scrosler[/MENTION] as each has provided us with amazing tools to return to stock or upgrade your device from 5.01/5.02 to 5.1, sans the need to revert to stock 5.01.

Please go to http://xdaforums.com/showthread.php?t=3066052 thread for flashable zips of entire 5.1 roms or modems ,or this Android File Host page from SCrosler for flashable 5.1 modems + bootloaders...https://www.androidfilehost.com/?w=files&flid=23050

https://www.androidfilehost.com/?w=files&flid=23050