How do I change the sleeping habits of a 3 year old

I would watch her intake of sugars before bedtime. (I'm sure you are already doing this though) I would cut out nap time altogether, and institute quiet time. (I do this with my son, who was having a hard time sleeping, basically he has to spend that hour that he would be sleeping, he spends it in his bed, looking at books quietly.) Also, what time is she waking up? I'd start waking her up a little earlier, if it's not working. There's no rule that says she HAS to go to sleep at 8:00, but it's better for everyone if she has an earlier bedtime. I would suggest moving the bed time to 8:30-9:00, and see if that helps. She could just be getting so worked up, that when she DOES get tired, it's difficult for her to sleep. ALso, watch her t.v. time and computer time, before bed, studies show it's much more difficult to get to sleep if you spend a lot of time at a screen before bed time. You could also put her to bed at 8:30, then allow her to stay in her bed and look at books for a 1/2 an hour, to wind down more. That way she will be more likely to fall asleep by 9:00. Hope I gave you some good ideas.