Bleeding gums is caused by infected and inflamed gums. This is due accumulation of dirt and germs which are the media for bacteria to live and this causes infection of gums and in turn bleeding.
Proper brushing technique has to be followed with other aids like flossing and mouth rinse.
Routine dental visits are mandatory, as this would help you to maintain good oral hygiene. Professional cleaning aids in cleaning the areas which could not be accessed by us with regular brushing.