Flaw. Want. Need. (my not-so-secret recipe to writing)

Poppy teaching a crime fiction workshop at Logan North Library last week.
Craft - How do you come up with character personality sketches for your books - do you plunge in and let your characters develop on the page, use real life people as inspiration, turn to personality frameworks like the enneagram? Especially for those who've written a lot of previous books - how do you keep your new characters from looking and feeling like your old ones? 
Initially, I thought this was a hard question to answe...