There are lots of good tips out there for people who have trouble sleeping — how and when best to eat, drink, exercise, etc. But let's focus on how light can make an impact.
Make Your Evening Dimmer. Low light stimulates the body's production of melatonin, the sleep hormone. After dinner, turn down the lights in your home. Switch out the bulbs in your bedroom for low-wattage lamps, or even light a few candles to get your brain in the mood for bedtime.
Turn Off the Screens: According to the New York Times, "the light from a computer screen or an iPad has roughly the same effect as the sun." And, since sunlight is the brain's primary signifier of 'awake time,' backlit screens should be banished from our evening rituals. This is definitely the hardest piece for me — I even commit the cardinal sin of checking my phone when I wake up in the middle of the night (you never know when it's going to be your move on Words With Friends)! But clearly that has to stop.
Blue is Bad. Of all the light to have in your bedroom, blue light is the worst, apparently because our brains interpret it as sunlit sky. So that alarm clock with the 'soothing' blue light might actually be messing with your head! Same with the classic blue glow of the TV. Try to turn screens off at least an hour before bedtime, to give your body a chance to adjust, and maybe swap out your blue clock for a differently hued display.