Part 1: How does David build his 37 Mighty Men militia?

In order to do this story justice, I figured to break it up into sections: How then Who. Basically, after David kills Goliath in 1 Samuel, he’s on the run/gets married/has kids/becomes King leading to 2 Samuel 23 when his Mighty Men are listed. So, the first part of this series will be documenting how his Mighty Men will join him and from where. Hope you dig it!