What does Odysseus do in book 9 that shows that he is a good leader?
In Book IX, Odysseus recounts stories from the time immediately following the Greeks' victory in the Trojan War. He and his crew first stop in Ismarus, killing the men, raiding the city's treasures, and raping the women; Odysseus advises his crew "swiftly to fly," but they do not listen. Instead, they get very drunk and pass out. The men who'd fled the city had run for help, and those men attacked Odysseus's crew during the night, killing six from each ship. His wise advice to his men is no less wise for their not having heeded it. His forethought and sagacity make him a good leader.
When they go to the land of the lotus-eaters, Odysseus -- intelligently -- sends only three men ashore to get a sense of the inhabitants. When they eat the lotus, they no longer want to go home. They want to stay there and eat lotus fruit forever. Odysseus, knowing their true desire to go home, physically forces each of them back to the ship. He looks out for their best interest even when they do not know it themselves. His intelligence and loyalty to his men make him a good leader.