Write a story in which two characters who don’t get along have to work together to come up with a mutually-acceptable solution. Use a third-person omniscient narrator to tell the tale in order to show both characters’ perspectives as the story progresses; this will allow you to depict both action and each character’s reflection on their relationship. Perhaps two mortal enemies must defuse a bomb before they both explode. Maybe a feuding mother and daughter need to rally for their husband/father’s surgery. Or it could be two high school friends who had a big fight want to reconcile before graduation.
Give this exercise fifteen minutes of your time, though if you’re truly getting into your characters it may take you longer to really get the story going.
Write it up and see what happens,