If you're struggling with one of you characters, try writing a letter as your current character to their older or younger self. Think of what they might want to tell their past or future self, this might help you pinpoint what's important to your character.
Your protagonist has just been bequeathed $5 million dollars. The money came from an anonymous benefactor who wants your protagonist to donate all of it to five charities. How does your protagonist react? In a short story, write down what would happen next.
It's impossible not to put some of yourself and your own life into your writing. But when you're writing about characters who you don't share much in common with, it can be tricky to authentically capture their "voice" and point of view. To develop this skill, fill out this character profile and base it on yourself. Then fill out a second one and make it as different from your own as possible.
Select a scene that involves 2-3 characters. Write a paragraph from the point of one character. Now write the same interaction from another character's point of view. For example: your paragraph could involve the point of view of a convenience store clerk contrasted with a customer's point of view of the same incident.
Write a pivotal scene in your novel from a different character's POV. For instance: at a funeral, you may have written the grieving widow's thoughts and feelings. Write about that funeral from the deceased husband's POV, the eldest son's, or the step-sister's.