These are some of the best resources I have found for optimizing games in Unity. The Unite videos have some good tips that are not in the manual. Be sure to take a look at them.
Make sure you have read this section of the Unity Manual http://docs.unity3d.com/Manual/OptimizingGraphicsPerformance.html
Here are some good videos in the Unite archives
2012 Performance Optimization Tips and Tricks for Unity
2014 Mobile performance poor man’s tips and tricks
2014 Big Android: Best Performance on the Most Devices