Readers remember characters, not plots. Think about your favorite books. You probably remember how the characters made you feel more than the specific events.
When creating characters, give them flaws. Perfect characters are boring. Give them goals and fears. Give them unique voices and mannerisms.
Show Character Through Action
Don't tell readers your character is brave - show them doing brave things. Don't say a character is selfish - show them making selfish choices. Actions reveal character.
Dialogue is also powerful for characterization. How someone speaks - their word choice, their rhythm, their slang - tells readers who they are.