Flossing isn't just about removing food stuck between your teeth; it's about removing plaque below the gumline where your toothbrush can't reach.
The C-Shape Technique
Don't just snap the floss up and down. Wrap it around the tooth in a "C" shape and gently slide it down under the gum tissue. This removes the bacteria that cause gingivitis. If your gums bleed, keep flossing! It usually means they are inflamed and need more cleaning, not less.