My first encounter with the law of attraction was when I first watched The Secret in 2011.
I have watched the film version of The Secret more times than I can remember since then.
The strongest lesson I learned from the book was the categorization of thoughts into two simple groups - positive and negative.
I like the fact that the main concept being promoted by the book was articulated from a plethora of standpoints - by experts in concerned fields.
As mentioned in the film (and also the book), it is important to point out the fact that the effects of the law of attraction requires time and consistency to become evident.