What changes did you make that resulted in increasing productivity, improving efficiency, or lowering costs?

Organise time and priorities

There are many a lot and I can not write down all the accomplishments here

And the experiences of colleagues good example

I advise reading the experiences of managers of Google Inc.

Good selection of the team members and motivating them can change alot of things.

If I need to talk about my personal career life, which fits well as an answer of your question, I will say that I deployed a self study plan, within last five to ten years, and I improved my productivity and lowered costs to achieve all of my earned certifications. Therefore, I am using for what I have been learned to do in a risk based and acceptable costs environment for performing an Information Assurance/Security tasks and duties of my assigned clients.