Honestly good sleep is earned, it is not just received.
Eating healthy (aka big breakfast with fruit, protein, fiber, and carbs. medium lunch- fruit and protein. small dinner- mostly protein. with snacks in between these periods will keep your energy levels optimal).
With good energy levels, you need to burn a significant amount of calories. When calories are burned at a good healthy athletic rate, your body will go from high intensity energy output to conservative mode. I recommend AT LEAST an hour and thirty minutes of exercise a day. When you exercise, always try to keep advancing in strength. Don't be someone who gets stuck at a plateau and cannot break it.
In conservative mode, your body will be much more relaxed and be in a very likely good and social mood. An hour from this should result in some fatigue as long as you don't consume large amounts of sugar. This means no fruit either! Save that for BEFORE you burn energy not when you want to sleep. Also consume no stimulants, caffeine, or other energy inducing consumables.
If you have pushed yourself and your body has used a lot of energy it will naturally (by instinct and recovery) NEED rest. You won't HAVE to sleep, you will WANT to sleep. It might even happen earlier than planned. If you aren't feeling tired you might not be exerting yourself as much.
Essentially, being healthy in what you eat and how you exercise will contribute to great sleep as well as being unhealthy will contribute to insomnia. If you come back saying exercising didn't work- poke yourself where you have been exercising. Is it sore?
Other strategies could include dissociative properties. Many people who have medical conditions (or some who use illegally) like to relax and fall asleep on prescription drugs like Xanax.
If I did not have a very athletic day (rare) I like to smoke heavy indica strain marijuana. I like it when its purple, that will put you to sleep fast as hell if you let it.
I have never used this method specifically for the reason of insomnia, but 1 beer always tends to make me sleepy.
Should be able to avoid using any substances as long as you exercise right and eat right.
now heres a fun fact:
The healthy amount of sleep every night for teens is 8.5 - 10 hrs.
One study has showed that only 15% of teens achieve this during the school year.
Be good to yourself