Little Miss' hair is ALMOST long enough for pigtails! We didn't quite make it all the way down to include all of the hair in the back. This style was helpful in getting all of the hair on the sides into the style, though. And if your hair model has longer hair, this could easily be continued down the back of the head to make (more complete) pigtails. I actually did this style on Little Miss for the first time just before she got her hair cut, and joined the two pigs in back to make a half-back instead of pigtails. You can do that, too! It's very versatile. (By the way, these pics were taken during a warm spell a couple of weeks ago... so she's not out shivering in the December cold. It was actually up around 60! And we weren't out for very long. ;) )
Part the hair down the middle. Part out a section at the front of the head as shown below; take not just the hair on top, but also the hair all the way down on the left (in this case). Tie it off with an elastic. I like to do all of the lefthand ponies in one color and the righthand in another color.
Now, part back towards the back of the head right behind that elastic for an inch or so. Then continue horizontally across the top of the head and down all the way on the other side of the head. Include the loose hair in front from the previous row, but NOT the elastic you already tied off. Tie this all off with another elastic.
Part again towards the back of the head for an inch or so, right behind the most recent elastic (yellow in my case). Continue the part down the left side of the head. This time, include the hair from the first red elastic (in my case) and tie it off with another elastic. The 'ladder' ponies are beginning to take shape.
Continue to do the same thing now, alternating sides. If you're good, you might be able to choose your parting angle such that you hide the little inch-long parts (that go towards the back of the head) underneath the ponies. I didn't quite manage to do this this time. Oh, well. Next time's a charm!
Try to make the last sections thinner, so that the very last elastics on each side are even with each other. And you're done!