General Colin Powell provides 18 lessons on leadership based on his experience as Chairman of the Joint Chiefs of Staff. Some of the key lessons include: being responsible means making difficult decisions that will upset some people; leaders must address problems brought to them by their team; don't be swayed by experts or elites and instead focus on results; and attracting the best people is key to accomplishing great things. Powell emphasizes that effective leadership requires making tough choices, focusing on execution over plans, and simplifying solutions so everyone can understand.