It's not easy to answer your question simply, but I can say it started for me with just remembering to consider, "What does this other person want?" There are many ways this is described in life, such as "Put yourself in their shoes", but I was shocked to realize how rarely I approached situations with that consideration.
The stories used for illustration are rather quaint and wordy, but they do the job nicely. Plus, we tend to respond to anecdotes better than just rules.
It's a short book, and IMO something that should be taught (and practiced) as a class in middle school.
When you were doing the Pimsleur courses, how far did it help you progress? Did it stick with you?
I didn't stick with it, however, because I moved to Netherlands :).