Make Characters More Realistic
Brainstorm all the qualities, weaknesses, quirks and relationships your character has. This will help you to create a more convincing persona.
For example:
STACEY
Sporty, vegetarian, stubborn, persuasive, likes to get her own way, considerate, is in love with Billy, hates cheese.
BILLY
Head of the football club, is Joanna's brother, likes to hang out with Stacey, athletic, usually calm, accident-prone, loves pickles.