God chose Saul to be king. See here and here.
Saul was a humble person. He told Samuel that he wasn't worthy of the office. At the convocation where Saul knew that he was going to be named as king, instead of getting a new robe and hiring a band, Saul hid himself away from the people. When he was named king publicly by Samuel, and acclaimed by the people, there is no record that he started out to build himself a palace, or hire bodyguards. Instead, he apparently went home to the family farm and went back to work.
Saul had some sort of conversion-like experience, and prophesied.
But Saul made some terrible choices.
The first one recorded is when he took upon himself to offer a sacrifice to God, rather than waiting for Samuel to do it.
Another bad choice was when he was told to lead the Israelites against the Amalekites, and to destroy their entire population, and their animals. Saul didn't kill the Amalekite king, nor did he and his soldiers kill all of the animals. He told Samuel that the animals were kept so that they could be offered as sacrifices.