King Saul of israel - general overview
The people of Israel wanted to be like the surrounding countries and have a king over them which was human that they could see, instead of having the unseen God lead through prophets, judges and priests. God obliged their requests.
Saul was a strapping young man, the most tall and handsome of the land. He obeyed his father when sent to retrieve the lost donkey. He repented of sins committed against God. Anyone, would have chosen such a gentlemen as him to be king. Samuel the prophet was instructed to pour the oil of gladness over his head and make him the first King of Israel.
It didn't take long for this young man to begin to believe that his way was just as good as God's way. He outright disobeyed the commands given him by Samuel from God. For these sins, the kingdom was taken off him, and given to David although it would be years before it came to be.
Saul made a few major errors. He was afraid of the advancing army and Samuel's perceived delay of arrival, so he made the offering to God himself instead of waiting for Samuel to do it. He allowed his men to take plunder from the war and didn't kill the king when he was told to destroy everything. He went to a seer to summon Samuel from the dead to inquire of a military attack against another country. All of these errors show that his will to do what he pleased was greater in him than his desire to honor and obey his God. Because he didn't honor God, it cost him the kingdom.