There's a Sufi meditation, focus on the air going in and out of your nose as you breathe, and try to think of nothing else. I find that helpful, though if my brain's really hyperactive, it's not enough.
Sensory issues keep me awake sometimes (randomly itchy skin), so I apply remedies.
I try to avoid doing hard brain work before I go to bed. Ideally I'd do something artistic. Hard to achieve because I tend to hyperfocus and intellectualise everything.
I remove unpredictable external sounds by reporting noisy neighbours and by using a pink noise machine or an electric fan to drown them out. There's something very soothing about those noises. It used to help my son sleep when he was a baby, if I switched on a hair drier.
If you're lucky enough to have a bedmate, sex can help.
Some folks are kept awake if they eat before bed. I'm the opposite, I sleep very well on a full stomach, and if I haven't eaten, I feel especially hungry and restless in bed, and have to get up and pig out, which takes ages, I even have to clean my teeth all over again.
Physical exercise helps me sleep.
I've tried alcohol. It can help me sleep but it makes me feel really groggy in the morning.
In an ideal world, if you're not sleepy, don't try to sleep. Get up and have fun, and sleep when your body tells you it's bedtime. In a sense, the only problem is morning appointments, but we can't all avoid those, what with jobs, school etc.