my hair started to dread naturally after i killed my hair (two and a half years of obsessive bleaching and dyeing, changing hair colours once every 2 weeks). i sped up the process a bit by tying it bits of string in the fron and on the sides and added some wax every now and then, but otherwise my hair did just take control of the situation. the first time it took about 6 months to get a full head of dreads, and then on a whim i cut them all off (silly me). after my hair grew out a bit, they started dreading, again. this time i cheated, 3/4 of my head is shaved so it didn't take as long to dread.
the only problem is, since i let them grow in as they pleased, some have decided to stick out at strange angles. i tried using string and knotting the stray hairs around the base and in other areas. it worked fine on some but on others it just got worse.