On average (huge disclaimer here...I said AVERAGE) a person's sleep cycle is about 6 hours. In that 6 hours you go through roughly 5 stages of sleep, starting with the most refreshing and light sleep to the longer lasting and deep sleep (when REM happens).
If you get into a regular sleeping schedule, this stays in harmony and if you get a solid 6 hours of sleep the better. Remember, the earlier you go to sleep it works better since physically your body works harder to stay awake after dark. Waking up with the sun is great since it matches your bodies natural waking process. However if you are in an unstable sleep cycle, it gets harder and harder to enter the first stage of sleeping see it through to the end of the 5 stage.
Now to help you GET to that first stage, I recommend the following:
No TV, phone or computer for at least an hour before you try to sleep. They are all mental stimulants that will keep your brain chugging even if your body is exhausted. Calm relaxing music can help as long as it's not main focus (again, it can stimulate your noggin').
Alcohol/Tobacco is both a mental stimulant and muscle relaxer. You feel tired after having alcohol, but your brain gets a charge. Some people are really good at turning off their brains, others aren't. Find out if you can sleep better with or without alcohol. (Don't know about weed, never tried it and never researched it's effects on sleeping)
Mentally gear yourself down. You can't be workin' hard at a paper or doing research and then expect to hit the sack and knock out some z's. I would suggest taking the alcohol (if you so choose) at this point rather then right before you sleep. It'll force your body to relax which in turn can make you sleepy. If you time it right the alcohol's effect on your brain can wear off right before you sleep.
Last but not least there is the tried but true torture method. When you have a weekend or a really easy morning you can afford to bomb, stay up the entire night before and do your regular stuff during the day. This will utterly exhaust your body and mind, and use up any spare energy you would otherwise use to keep you awake (unintentionally, of course). I end up using this one most often. It SUCKS like anything at first, but it gives you blank slate to start working that on the sleep schedule.