I can't remember where I saw this idea, but I just loved it. To start, divide the hair into 2 sections like you would for pig-tails. Pick up your first section a couple inches in, and braid forward, turning the braid at the forehead and low past the ear. After you finish both sides, join them up to complete the heart.
After a little trial and error, I figured out that the shape stands out much better with an inside-out braid, pulling the section of hair up instead of down - essentially braiding backwards.