
Aromatherapy
Lavender essential oil in a diffuser is great for this purpose. Some people also respond well to eucalyptus or menthol scents. Get a diffuser (the type with a tea light candle below and use real essential oils up top in water), and see how that works for you. Combine with relaxing music to aid in getting yourself ready to drift off.
Herbal/Homeopathic
Melatonin -but before you take these (or any herbals,) check with your doctor to make sure it's okay; and as with any meds, call your pharmacist to make sure there aren't any drug interactions you may have or need to be aware of. (you'll need to tell the pharmacist every medication/herbal that you take currently.) There may also be some homeopathic things that can help with falling asleep- I'd make a call to your local health food store and ask them what they have that might help too.
White Noise
A lot of people have a fondness for white-noise sounds when it comes to helping them fall asleep- not only does it muffle out other noises, it can help put you into a "trance" (sort of) where you're off in your mind somewhere. Often those noises mimic the sounds of the womb, and even as adults, we find it really comforting. Also, it can aid the person in "transporting" themselves somewhere else in their mind to a specific "place" they develop that relates to each sound. There's an awesome program for the iPod touch/iPhone that gives you sounds and songs to work with and combine in any way you like-- I used that program to create all kinds of things, there's one that reminds me of my grandparents house I used to spend a lot of time at as a kid- very fond memories and a very calming, welcoming sound combo. Perhaps look into something like that- they sell white-noise machines as well, but be sure to listen before you buy- that way you'll know whether or not you hate the sounds prior to wasting the money. Any monotone type noise is good though- it quiets self-chatter and busy minds. (Or music sounds- it doesn't specifically have to be monotone.)
Distraction
A lot of people find reading a good way to distract the mind and make them sleepy- it'll ease your mind into another place as well, you're more inclined to wonder what's happening next in your story than think about what ever is remaining on your mind from your day.
Word games work for me too, anagram type things. Not sure if anyone else gets sleepy when playing with words, but I suppose it's worth a try.

If too much household/roommate noise is your problem...
Go to the hunting/fishing section at a Walmart or wherever and get some of those inner-ear plugs used for shooting/hunting. Then go to the bedding section and get one of those not-shaped/formed (you'll want the regular fluffy type instead) memory-foam pillows. At night, stick the plugs in (which just kind of make the noise seem to be a lower decibel but you can still hear it), then put the fat, fluffy memory-foam pillow over your head & ears. (if you sleep on your side- if not, start trying to fall asleep that way, once you get to sleep, if you shift onto your back, the noise probably won't wake you at that point.)
-Also, consider including the "white noise" option above. Most of the white noise machines and iPhone/iPod touch applications have timers that will auto-shut off after you drift off. (At a pre-set time, that is.)
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Stuff to avoid:
1. Caffeine. Stop all caffeine consumption for the day by no later than 4:00 pm. None- not even chocolate. Caffeine is a stimulant and not only does it assist in keeping one awake, it also stimulates the bladder, leading to overactive bladder symptoms while you're trying to sleep.
2. Exercising right before bed. The effects of exercising before bed are still subject to scientific controversy, but I do tend to believe that it is not going to yield the desired results for "feeling" tired that would be conducive to sleep. If you can get all the exercise in during the afternoon/morning and get yourself considerably physically exhausted, that should do the trick when it becomes bed-time. But otherwise, exercising at any time releases adrenaline and other hormones that, while you might feel "tired", do continue to surge throughout your body for quite a while after completing your exercise routine. It's very different to want to flop down on the couch and rest verses close your eyes and drift off to sleep. (Though this fact of adrenaline affecting ability to fall asleep has been scientifically contested. When it is tested, though, it's on ordinary people who aren't suffering with sleep disorders, so it's at least safe to say it's not a "good" manner of getting yourself into being ready to slip off into a sleep-state.)
...Hope that helps! :28:
~Bright Blessings and Pleasant Dreams~
*MoonStone