I've had trouble getting the recommended amount of sleep (between 7.5 and 9 hours, per sleep researcher James Maas — fun fact: he claims to have invented the term "power nap") for most of my life. At present, I don't typically have issues falling asleep after I go to bed, but I'm a light sleeper and often wake up around six, finding myself unable to fall back asleep. It's relatively easy to find online coverage of research linking lack of sleep to obesity, cardiovascular disease, and other diseases. Much of it mistakes correlation for causation, but I'm convinced that I ought to try to get more sleep to avoid mid-afternoon drowsiness even if there are no other benefits.
I read Maas's latest book, Sleep for Success, but didn't particularly care for it — here's my review on Goodreads. That being said, I still found some of its information to be useful. Here's a summary of what I've tried, both from the book and not:
Going to bed earlier - If I go to bed past eleven, I don't have a chance of getting more than 7.5 hours of sleep; I'll wake up early, tired but not sleepy. If I go to bed around ten, I have much better odds of getting eight hours or more.
Avoiding artificial light - Maas recommends against using electronic displays just before bed; most are heavily shifted towards the blue end of the spectrum and can apparently trick our brains into thinking that it's still the middle of the day (I haven't tried to find any research here, though). I've been using the program Redshift to gradually adjust my displays towards dimmer red colors as the day progresses. Intentionally messing up my monitor's colors was a bit painful at first, but I find that I actually prefer the change now. f.lux is the closed-source inspiration for Redshift; I haven't tried it. Maas also recommends reading before bed (as long as it's not something especially thought-provoking), but intentionally dimming the room lighting to induce eyestrain.
Drinking water - I already wake up at least once or twice in the middle of the night; I've found that having a few cups of water around 3 or 4 in the morning (late enough that I won't need to wake up to go to the bathroom) seems to make it less likely that I'll have a sleep-preventing headache if I wake up around 6 — presumably, I'm getting dehydrated otherwise.
Playing ambient noise - I've found that living in a busy area or having a stomp-walking, loud-talking upstairs neighbor can be responsible both for making it hard for me to fall asleep in the first place and for waking me up after I do. Most music is too distracting for me to fall asleep to, and ambient songs that aren't distracting are usually too quiet to block out the outside noise. I've had success with plugging my phone into a pair of speakers near my bed and playing ambient noise in a loop. The Freesound Project (free account needed to download, I believe) was a huge help here. I currently use a slightly-edited version of this track, a recording of rain falling into a stream.
Darkening the bedroom - I'm fairly light-sensitive, so morning sunlight coming in through the windows doesn't help my odds of falling back asleep. I've found San Francisco's apartments to have a dazzling array of different window sizes; the only consistency is that they're all taller than most window coverings that I can find in stores. I don't want to spend a bunch of money on curtains or blinds that'll be useless if/when I move.
I've tried several different options, like wearing a sleep mask (too easy to shift off of my eyes, and having something resting on top of my nose bothers me), room-darkening curtains from Bed Bath & Beyond (expensive, not particularly room-darkening, and likely to leak lots of light around the edges) and room-darkening roller shades from Ikea (really bad at rolling, and they curled inwards at the edges almost instantly upon exposure to sunlight). I eventually discovered Redi Shade's ultra-cheap (I think I paid around six dollars per window!) paper window shades. They're not as bad as they sound; they look sorta Japanese-like to me and are extremely easy to install (cut to desired width and length and stick on window frame). I went with the "room darkening original" model for my bedroom. They're actually more effective than the previous coverings that I've tried, but still not opaque enough to keep out the morning light.
I finally got serious last weekend and went to Discount Fabrics. It took some time to find a long-enough spool (I needed almost nine yards to cover two windows and a pair of glass doors), but I eventually went with a vinyl-backed fabric. I'd tried to take the making-my-own route before, but it's been my experience that anything that's just cloth as opposed to being vinyl on at least one side is going to let a bunch of light through.
Along with the fabric, I bought a ten-dollar pack of grommets. It took a few hours, but I eventually got all of the fabric cut to the correct dimensions with grommets hammered through the top corners. (Useful tip: before you start hammering, make sure that the grommet setter didn't come with an eyelet accidentally stuck on it. It may look like it's part of the setter, but it's not, and it'll get stuck inside of the eyelet that you're actually trying to use, and you'll get really frustrated and spend about fifteen minutes using two pairs of pliers to yank the setter out of the stray eyelet and using a pair of wirecutters to cut the eyelet off of the other eyelet that you've hammered it to. Or so I hear.)
Finally, I drove wood screws into the wall for hanging the shades. At night, the room is pitch-black. In the morning, a bit of light leaks around the shades (I left three inches of overlap beyond the windows' dimensions but the sill pushes the shades out a bit), but it's not enough to wake me up. Success!
Update: Almost immediately after publishing this page, I got email from Niall Cardin with more good advice:
After various efforts I decided that the things which made by far and away the biggest difference for me were
(1) Removing light (~75%)
(2) Reducing sound (~25%)
Nothing else has clearly impacted my sleep.
I used to do blinds and talking to my house-mates. However: learning to be comfortable with earplugs and a sleeping mask have proved to be a much more flexible/portable long term solution.
I think it takes quite a lot of effort to find a decent sleeping mask, (they're nearly all too small for me), though some nice adjustable ones do exist. As for ear-plugs there's a few good options, and this seems to be quite personal. I've settled on about the 5th set I tried :)
Do you have any sense of how much Redshift has helped? My guess is that it doesn't make nearly as much of an obvious difference as removing light from the room?
The other major thing that I'm sure you've noticed is: How much is on your mind - managing stress/work, or other things you can't turn your mind off to, makes a big difference.
I'd say that Redshift mainly helps me get into a better mindframe for falling asleep, in largely the same way as the stress/work stuff that Niall mentions (and Maas in his book, too — in particular, he suggests keeping a notepad next to the bed to write down any thoughts or concerns that come up while trying to fall asleep, so that they can be shunned until morning). I already didn't have much trouble with the falling-asleep phase, though, apart from isolated instances where I'd be obsessed by some programming issue and finally need to get up to work it out at the computer.
Making the room dark seems like it's been the biggest factor for me (assuming that I'm going to bed early enough), too, although my sample of nights since putting up the shades is much too small at present to make any definitive statements (n=2). Honestly, it seems like there are other factors (probably mood- or health-related) that I'm just not picking up on; I can remember long stretches where I was averaging eight-plus hours per night despite conditions more adverse than the present ones. Ho hum; more opportunity for research, I guess.