My girls love doing this and we end up doing it about once a week. It's great because then I have a little less stress about doing their hair in the morning before school. (Did I mention they start elementary school at 7:30 here?! Way too early!)
To do this you need to have wet hair, so it is better if you do it after shower and baths. Comb through the hair. To keep it from being frizzy in the morning I put in some mousse. I like to use
Tresseme Extra Hold Mousse, it keeps the waves in all day, sometimes they will last a couple of days, and it keeps the hair from being frizzy.
After you have combed the mousse through the hair divide into four sections. The more sections you do, the small the braids and the tighter the wave will be. The less sections you do, the bigger the braid will be and the looser the wave will be. I have found the four braids work really well, the braids are small enough you get a good wave and they have enough time to dry overnight. If you do too big of braids they might not have enough time to dry overnight.
Take the first section and do a french braid all the way down .
Take the next section and braid it. Continue to do this for all sections of hair.
Then you let it dry overnight.
In the morning take out the braids, use your fingers to comb through them and you are left with gorgeous waves! Now if you want you can pull it into a ponytail, half ponytail, or just leave it down. It looks great either way!