Proper use of dental floss:

First cut about 18 inches of string and wrap it around the middle finger of both hands.
Place the thumbs of both hands on either side of the floss so that about an inch or two of floss remains in the effective area.
Gently run the floss between the teeth in saw-like motions.
First clean the tooth and the depth of the gingival furrow.
Then do the same with the second tooth and gently pull the floss between the teeth.