The use of certain habits is clichéd so consideration may be needed if you are going to write a vibrant and unique character rather than a caricature.
Bad habits based on body exploration - making noises with or delving deeply into nooks, crannies - can be provide hours of creative fun but remember the reader may be more easily offended.
This list of bad habits could be used to show internal conflict or character traits. They could also be used to show other character's temperament or attitudes.
13 BAD HABITS:
Making destructive comments: “witty” sarcasm
Sleeping with make-up on
Chewing on the inside of cheeks or at the lips
Games playing - portable, on a phone
Drumming fingers on objects – tables, window frames etc
Reading in the dark
Eating chocolate/particular sweets
Verbal tics – Like, you know. OK. Alright. That’s mint!
Hair pulling or twirling
Swearing including using irritating anti-swearing techniques “Oh! Garibaldi!”
HOW’S IT GOING, WITH YOU?
hapless, happy, harassed, hard-hearted, harsh, hasty, hateful, haughty, hazy, headstrong, helpful, heroic, hesitant, high spirited, honest, honourable, hospitable, hostile, humble, humiliated, humorous, hysterical