What keeps me awake is worrying about.... everything in life. I've gotten much better over the years. One of the things that is most helpful to me is to watch a show I've seen several times before, like scrubs, futurama, dilbert, etc... They don't have anything on them that will keep me up and worried. I have the screen on the tv turned down in terms of brightness and contrast. As I'm watching the tv and not moving it gradually makes me sleepier. I'm in a dark room, and feel safe, I decrease the volume a few notches as I lay in bed. I put a sleep timer on, or my current tv automatically turns off, so it takes that extra step out. This routine helps my body be instantly associated with it's sleep time. I set several alarms on my phone as well so I won't have to check it a 100 times to make sure the alarm is set, since one of my alarms should function. If you're on your computer at nighttime or phone turn the brightness all the way down, too. You're making a routine that if it puts you to sleep at all your body might eventually associate with sleep every time.
I studied abroad in Paris for a semester back in college and basically lived off of crepes.
