The Knotty Pony: Part your hair down the middle and divide into two sections. Tie the two sections in a knot. Then tie the ends together into another knot and combine the two ends and secure the knot with bobby pins at the nape of the neck.
We love half-up styles for their casual prettiness and minimal upkeep. Adding a barrette (instead of the expected hair band) immediately updates the look, adding a little bit of fanciness (without looking like you tried).