I have a running to-do list that I consult with constantly throughout the day. Pretty much at the end of every task. At the moment I am using MicroSoft OneNote, but a paper and pen works just as well.
The approach I use is based on the GTD (Getting Things Done) methodology developed by David Allen. His book really changed the way I work and as he says, put me on the road to the “Art of Stress-Free Productivity”. I generally give this book to every one of my staff.