To build an efficient pendulum that retains 75% of its amplitude after one minute, factors such as the density of the pendulum bob, string length, and design shape are crucial. A high-density bob minimizes air drag damping relative to mass, while a longer string decreases the pendulum's frequency, further reducing damping effects. The shape of the pendulum, like the pancake design used in clocks, is also important for minimizing air resistance. An experiment involving coupled oscillators can demonstrate energy transfer between pendula, highlighting the interconnectedness of their movements. Understanding these factors can significantly enhance pendulum efficiency.