When I was young, I read books and articles with ideas about how to be effective. I had gracious mentors and teachers who gave me insights from their experiences which I could apply into my own life.
And I did. I read David Allen's Getting Things Done and now keep all my tasks organized in OmniFocus. Because I enter tasks from my phone and review them weekly, I never worry about forgetting something.
I read Tim Ferriss's 4 Hour Workweek and now recognize how to apply the Pareto principle to accomplish more in less time by eliminating the trivial in favor of the critical.
My mentor Patrick introduced me to the agile software development methodology. Now I don't even think twice when I organize my client projects into user stories and allow the product owner to prioritize their implementation.
Merlin Mann's talk Inbox Zero at Google in 2007 led me to keep my email inbox empty ever since.
After reading Vicki Robin's Your Money or Your Life, I learned the importance of tracking every penny that comes into or goes out of my life. It's become a keystone habit for improving my finances.
These ideas are simple to understand, but can take years of conditioning and practice to become habits. When I first heard these ideas, I would parrot them as the holy dogma of how to be effective. But years on, I realize they're merely lanterns lighting the way. You still have to walk the path.