Getting professional cleaning done atleast once in six months is as important as brushing your teeth twice daily. Then rule out any other problems like sinusitis and gastric irritation which can also cause bad smell.
Next Steps
Professional scaling by a dentist and then follow it up if there is persistent bad smell.
Health Tips
Onions and garlic are food substances which add to bad breath. Brushing and tongue cleaning atleast twice daily. Keep yourself hyderated by sipping water at regular intervals.