Personally I've found a good amount of physical and mental stimulation is required to get my sleep schedule in order, otherwise I'm like you and can't fall asleep till 3, 4, or 5 AM and end up sleeping till noon or something. I often even will try to go to bed early but simply can't fall asleep.

That being said, if I get about 30 minutes of exercise in my day and a healthy dose of mental stimulation as well (having to think hard at work, socializing with friends, trying to learn something new), I usually get tired and will be able to sleep well and not want to oversleep either. Like someone else said, it's been important to really go to bed as soon as the sleepy window hits, otherwise I usually will end up becoming awake again and not be able to go to sleep again till 3 or 4 AM.