I posted recently about looking at reviews for the Nexus 6 on Amazon, and there was one recent review in particular that caught my eye. The person in question talked of rooting his co-worker's Nexus 6 and tweaking it to the point where the device now achieves great battery life. I asked him what he had done in short, and he directed me to his post on XDA. Since I'm a member, I searched his name, and came upon his detailed post. These tweaks, however, can work on any rooted Android device. Here's the post, for those who are interested:
http://forum.xda-developers.com/showthread.php?t=2357417
http://forum.xda-developers.com/showthread.php?t=2357417