Usually I have no trouble going to sleep b/c I go to bed relatively late when I get tired. If you have trouble going to sleep, maybe try doing something active late in the afternoon to let off all your energy, and then you'll be more tired by bedtime.
I have no problem staying up until 4 in the morning, but if I try I can go to sleep anytime after 10. I hate sleeping in past 9 in the morning though. Even if I go to sleep late. I can function on small amounts of sleep every now and then, and in fact it actually makes me more hyper than normally, haha.