Not getting enough sleep can sometimes be a bad thing. Getting too much is just as bad.

Steps

Go to sleep at your usual time. Don't go to sleep later and expect to wake up in the morning earlier. You'll want to sleep in and thats the thing you don't want to do.
Set an alarm. It doesn't have to be too early, just enough to get anywhere from 7-9 hours of sleep. Do this for at least a month and your body will get used to waking up at this time so you won't have to use the alarm.
Tell other people. If you don't hear your alarm or if you forget to set it, make sure there is somebody around to make sure you don't sleep in too late.