We all have history. No matter where you start a story, you are never starting at the beginning. Well-handled exposition can bring perspective, dimension and needed context to your story.
The hardest thing when starting to write is to stop your story turning into a biography, because the minute you start, you’ll want to write “Wait until I tell you about her father… and what she was like at school… and the day she was born.” Don’t fall into this trap of ‘establishing’ things. It is always better if your reader has to wonder what’s going on, than to have everything in black and white.
Having said that, the backstory is often the trigger that starts the story; the moment of decision unknown to the other characters that starts the ball rolling
Keep it brief. Bring in backstory when it has bearing on what is happening at present.
Use Arguments. Convert your exposition to ammunition and let your characters use backstory to win arguments, saving the most damning piece of information for the last line. It can be information given as an emotional outburst turning frustrations into information like ‘I’ve been paying your drinks bill for ten years!’’ or in turn it could be used to justify your character’s actions. “Look, this is just the way I was taught.”
Use Humour. Exposition can be more interesting if said with humour revealing your character’s attitude.