After some general reflections on the nature of concentration (or samadhi), concentration practice, and its place and importance, we explore the nature of skillful effort. We particularly focus on the balance of "pro-active" effort and relaxation/ease, identifying a number of specific practice tips and suggestions that support development in both aspects of practice, as well as how to cultivate the balance between the two. [A clarification about terminology: There are two terms that have at times been translated as "effort”: (1) The 6th factor of the Noble Eightfold Path is “Right Effort” (same vayama); (2) Viriya is one of the Five Spiritual Faculties and one of the Seven Factors of Awakening and is often translated as “energy,” sometimes as “effort.”]