Duhigg's bestseller yet, find the time to read it or at least see the TEDx Teachers College talk below, which is taken from the appendix of the book. The book is an excellent read.
Here is a good synthesis from the author of the book:
"As a result, this book doesn't contain one prescription. Rather, I hoped to deliver something else: a framework for understanding how habits work and a guide to experimenting with how they might change. Some habits yield easily to analysis and influence. Others are more complex and obstinate, and require prolonged study. And for others, change is a process that never fully concludes." (pgs. 275-76)