1) Anxiety and/or Depression - Do you find yourself worrying about things that happened in the day or what is going to happen in the next?
2) Proper Sleep Hygiene - Are you winding down your evening, shutting lights off, avoiding electronics and excessive stimulation at least an hour before bedtime?
Each of these is a great piece of advice.
I have sleep problems for which I've tried all sorts of solutions, from Ambien, to melatonin, to valerian, to l-tryptophan, etc.
Ambien has always worked, but it's a diabolical medication that I wouldn't recommend. Too many strange side effects. However, it has helped with jet lag, and times when my sleep schedule is completely opposite where it should be.
If you find you need a supplement to help you sleep, have a chat with your doctor. Ask his/her thoughts on things like melatonin before jumping to prescription medications like Ambien or Lunesta.
I recommend the Calm app, which does some guided mindfulness meditation exercises to try to quiet your mind. We (people who care enough about technology to be posting here) tend to be very active consumers of information, seeking constant stimulation. That can be extremely disruptive at bed time. Calm has helped me clear my thoughts and get in a good mental state for sleep.
I would also download f.lux for your Mac, and use the night feature on iOS 9.3 when it is released. I find this to be helpful earlier in the evening.
Try regular exercise, it usually helps quite a bit. At least, it works wonders for me.
Another great tip. You should try to be as active as possible during the day, so your body wants to rest, and gives your brain as little say as possible in the matter. Even if you are just taking a brisk walk for 30 minutes a day, you should notice a difference in the quality of your sleep.
Most importantly, establish a pattern in your day. I find it astonishingly difficult to wake up any earlier than I need to. If I have no obligations until the afternoon, there is a strong impulse to sleep until shortly before that obligation. That takes some willpower and practice, but consistently waking up at the same hour helps you feel tired at the correct hour.