As a former PMP (just let it expire), some of the things I remember:

- Ask "Why" five times, not only when trying to diagnose a problem in root cause analysis, but I think it's good practice to ask that question several times from the outset of a project - make sure what you are doing really ties back to the mission and goals. If it doesn't, ask "Why are we doing it?"

- Work breakdown structures are incredibly useful. Rarely do projects go through that kind of forethought in order to consider the resource implications - time, cost, people - and assign projected values to each.

- Love Gantt charts and the ability to know whether or not a project is on time...or slipping...but, again, it's about directing project outcomes versus just executing and hoping for the best.