Cool, dark and quiet, at the same time every day including weekends. Everything else is secondary to those four.
Most sleep advice is about the hour before bed, when the useful changes are actually about the room, the timing and what happened earlier in the day. The room is the part people ignore and the easiest to fix.
What it covers
Every tip in sleep
Around 16C to 18C, which is cooler than most people keep a bedroom. Body temperature has to fall for sleep to start, and a warm room prevents it.
Usually a normal end-of-sleep-cycle awakening that you have started noticing, made worse by looking at the clock. Alcohol and a warm room are the two commonest aggravators.
The content matters more than the light. A phone at midnight is a problem because of what is on it, not mainly because of its colour temperature.
If you are still awake after about twenty minutes, get out of bed and go elsewhere. Lying there awake teaches your brain that the bed is a place for being awake.
A short nap, twenty minutes and before mid-afternoon, helps. A long one, or a late one, takes the edge off the following night.
It has a half life of around five hours, so a coffee at four in the afternoon still has half its caffeine working at nine. Stopping by early afternoon is the useful change.
This is general information, not medical advice, and it does not replace a GP, a pharmacist or NHS 111. Call 999 in an emergency. Full disclaimer.