Read a book or a magazine - I appreicate this is very old school. The reason is studies have shown that brain activity during sleep is better regulated after reading a physical book compared with reading a screen.
Have a hot shower or bath at night. When you get in all your blood comes to the surface of your body, so when you step out, your core temperature starts to drop. This stimulates sleep.
Go to bed at the same time every nights - it's possible to "programme" the body to get used to falling asleep at a certain time every night.
Yoga or light exercise can help relax muscles and release any tension.
Complementary therapies - these promote relaxing, reduce stress and anxiety and are therefore ideal for a good night's sleep.
Breathing exercises or medication - taking deep breaths helps the body switch off from the flight or fight more to rest-and-digest mode.