Step 1: Select floss
waxed - best for rough surfaces/restorations in the mouth that snag unwaxed floss
unwaxed - thinner, slips between teeth and under gum tissue easily, flattens out against the tooth, and makes a squeaking noise when tooth is clean
Kevlar - strong and slick, resists tearing on rough surfaces/restorations
braided - stretchy yarn-type floss especially good for large spaces between teeth
Try them and see what works best for you. The important thing is that you do floss.