The Nexus Root Toolkit is still the easiest way to Root your phone. It also does things like unlock your bootloader, install custom recovery, and flash stock images to unbrick your phone. The utility is able to find and download pretty much anything you need so this is a one stop shop for everything. Wugfresh has just updated it to version 2.1.1. The latest version adds full marshmallow automation for NRT functions, new system that doesn't really on modified boot images but uses TWRP's adb root shell instead, automated features now work in any build mode, nexus player scripts have been updated, and bugs have been fixed.
This one tool will work with every Nexus device and it does not matter which build of Android you are running. The utility also downloads and installs the proper fastboot drivers which means you don't have to install the full SDK in order for your phone to be recognized by the PC. Head to the link below to grab this toolkit.
via Wugfresh