The Pareto Principle, or 80/20 rule, is a popular principle that deserves all the recognition and bears repeating.
What is the 20% of the effort that can provide us with 80% of the result? How can we avoid 80% on the non-important effort that only yields 20% of the result?
Focus on the most important, get results/feedback, assess, then game plan for the next steps accordingly.
It is a simple, efficient way to analyze what types of actions you should be taking to move your projects forward.