Alternatively:
1. Establish a routine prior to bed and stick to it every time. Mine goes something like this:
A. 90 minutes before bed: Shower, and change into pj's. Turn down the bed and dim the bedroom lights.
B. Drink 1 cup chamomile, or chamomile-lavender, tea. Celestial Seasonings brand's "Sleepytime" or a similar product (there are several herbal tea companies that have sleep teas) also works well.
C. One hour before bed: Yoga practice. I use videos or sometimes just my own series of poses based on what feels right at the time. There is a ton of stuff out there.
www.yogajournal.com is a good place to look for poses and their "pose finder" function will help you search specifically for relaxing poses/poses to help you sleep.
Even just gentle stretching, with full and relaxed breathing, will help if you don't want to do yoga.
D. Meditation practice. Sit comfortably and take slow, deep breaths. Concentrate on your breathing. You may have thoughts buzzing around in your head; just let them go. Don't try to "catch" them or think about them, and don't let it frustrate you that your brain is busy when it's "supposed" to be quiet. Return your concentration to your breath and try to hold it there. Breathe deeply and slowly. It will take practice. Sometimes it is helpful to meditate lying down. Since all yoga sequences end with a savasana (lying on your back, resting), it can be easy to transition from this into a lying-down meditation.
Animus' binaural beats may help you here.
Also there are threads in here about meditation that talk about it in more detail if you'd like more information.
Usually by the time I come out of my meditation I am very mellowed-out and I go up to my bed which is already turned-down and looks very calming, with the lights dimmed and everything.
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That said, it is important to determine why you aren't sleeping because if you can fix that, then the rest will fall into place. Otherwise if you don't address that issue then anything you do will just be a "band-aid" solution. This is why the previous suggestions of keeping a journal or tracking your sleepless experiences are so important. If it's because you're thinking about what you have to do the next day, a simple solution can be to just write down a list for tomorrow. This helps me a lot. When my work is done for the day, before I start my little routine, above, I sit at my desk and think about all the things I need to do the next day, and I write them down in a little list, and prioritize them, and schedule them and whatnot (there is also a significant amount of color-coding that goes on, but I am a little OCD and that's a topic for a separate thread)

Once the list is done, I feel "free" of those tasks because I know there is nothing I can do about them until the daytime anyway, and I don't worry about forgetting them because they are written down and all set for me to attack when I wake up the next day.
If you're having trouble sleeping because your bedding is not comfortable, do what you need to do to fix that, as much as your budget allows--but prioritize it. Look into foam mattress tops, even just new sheets or different pillows. Are you too hot or too cold? Make adjustments to your sleeping environment until you are comfortable. If there is too much light in the room (I personally have to have a pitch-black cave to sleep well), invest in some room-darkening shades or an eye-mask to wear while sleeping. If there are noises, or silence, that bother you, find a white-noise machine or an ocean CD or something. Or some binaural beats. Or noise-cancelling headphones, or even earplugs. Do everything you can to make your sleeping environment something that will encourage sleep.
Also, check out your diet and lifestyle. No caffeine past noon is a good rule of thumb. Vigorous exercising too close to bedtime can wake you up, although for some people the "runner's high" is enough to knock them out. So you will have to experiment and see what works for you. It may be better to move your workout to the morning, or change the type of workout you do in the evening, depending. How is your carb and sugar intake? Some people have weird dreams and insomnia if they eat too close to bed; others need a little something in their stomach in order to sleep. Again, keep track of this stuff in your journal and examine what does and doesn't work for you.
If I had to guess, I would say it is probably some sort of anxious energy that is keeping you awake. Getting a handle on stress-management techniques will really help. Often when people can't sleep, they start stressing about the fact that they're not sleeping, and worrying about how tired they'll be the next day. And then they get frustrated and that makes the problem worse. Deciding where you're getting anxious and what triggers it will help a lot.
Good luck!