Do you find yourself taking a long time to fall asleep or waking up several times at night? Assuming there's no "bigger problem", here are some things you can do to improve sleep.
Let's call them: "what you see", "what you consume", and "how you feel"
"What you see"
Light in general causes your body to release hormones which suppress Melatonin (your "sleep" hormone), so you want your room completely dark.
But note also that a wave of light (blue light) emitted by electronic devices (TV, iPad, Iphone, etc) is particularly strong at suppressing Melatonin and should be avoided for 90min before bed. Read a book instead, and preferably use a red light bulb: red has been shown to help promote sleep.
"what you consume"
Avoiding stimulants such as caffeine is the obvious one. Caffeine has a half-life of 6-8 hours, so 6-8 hours after you consume it, half of the caffeine from that drink is still in your system. Beware of non-obvious sources of caffeine, such as soft drinks (not just dark colored ones), and some medication.
Switch to Green Tea in the afternoon/evening: what keeps you alert in green tea is L-Theanine, which, unlike caffeine, won't disrupt your sleep.
A remember that while caffeine and other similar stimulants may not stop you from falling asleep, they will disrupt your sleep pattern during the night.
People on a low carb diet or who are prone to low blood sugar may benefit from a tablespoon of honey before bed-time. Honey stabilizes your blood sugar during the night and prevents "crashes" which will wake you up. This is particularly important if you're stressed, as elevated Cortisol raises insulin, lowering your blood glucose.
"how you feel"
I've talked about Cortisol extensively in the past. The normal cycle for this "stress hormone" is: peak in the morning, low at bed time. For most of us though, certain behaviors and/or stimuli cause an increase in Cortisol in the evening, which severely disrupts sleep.
Aside from the obvious practice of avoiding stress-inducing behaviors at night (work, arguments, mental anguish), adopt a routine of "box breathing" for 5min when you get to bed: inhale deeply on a count of 4-5, hold for a count of 4-5, exhale "fully" on a count of 4-5 and hold for a count of 4-5. Keep repeating for 5min and you'll certainly feel the difference.
The other aspect you need to be aware of is room temperature. Aiming for a cooler bedroom (19-20C) has been shown to help induce sleep and maintain it.
Oh and don't forget to count sheep...