When I began my first novel, The Divorce Girl, I knew I was both basing this on my own life and fictionalizing it to get closer to the emotional resonance of what I had lived as a teenager. Fiction is like that: through the backdoor of imagination, you can enter the house of the story and get to know who lives there and what it all means, sometimes in far more telling ways than if you knocked on the front door of a true story.
Here are some strategies to fictionalize real life:
Take the Frame and Put In All New People: For my novel, I started with the frame of the story: teenage girl's divorcing parents refuse to leave house for a year, craziness ensues, and then mother and other siblings move out (leaving the girl to be a teenage housewife to her father) before the father remarries, and a whole new family moves in. I then inserted all new people: some matched up to my own experience (the father, mother, teenage girl), and some didn't (the Holocaust survivor housekeeper who works for the father's second wife). The more I revised, the more the new characters came to life, and as with most fiction, the characters then directed the nuances and direction of the story.
Place a Person In a New Story: You can also do the opposite: take a person (you were or knew), and change some characteristics (to make the character more her/her own person), but then insert this character into a new story. Have a vivid person you met when you were six who changed the course of your life? Move him to a new city, new time, new story, and see what happens. Remember a great-aunt who was, no pun intended, "a real character"? Put her into modern-day St. Louis, working at the Botanical Garden as a young woman, and see what happens.
Take a Page from Mythology, the Bible, or a Fairy Tale: There are tremendously rich mythic stories all around us that are ripe for the plucking. For the novel I'm currently revising, I've taken the story of Miriam from the bible and set it in contemporary America, wandering our political, spiritual desert for 40 years. Many great novels out there draw on biblical, mythic or fairy tale characters, storylines, even settings (think Anita Diamont's The Red Tent as well as Jane Hamilton's The Book of Ruth).
Tell a Resonant Story: The story you lived surely resonates with other stories. The story of a girl, growing up with a father who beat her, for example, could resonate with the story of a woman trying to leave her abusive husband. Writers have been looking to resonant stories forever. Alice Sebold, for example, wrote both a memoir and novel that resonated with her own painful experience: The Lovely Bones, her novel, is based on a young woman who was raped and murdered; her memoir of surviving rape, Lucky, is based on her story. Look for a sister-story that allows you to share the heart of your own.