To build an effective spring launcher, it is crucial to understand that not all energy can be transferred to the ball, as efficiency limits this transfer. The method of attaching the spring to the wood is essential for maximizing energy transfer. Using rectangular wood is a practical choice, but the specific design and attachment method will significantly impact performance. Proper alignment and secure attachment of the spring will help ensure that most of the energy is effectively converted into kinetic energy for the ball. Overall, careful consideration of materials and design is key to achieving a successful spring launcher.