If you haven't started sleeping after about 15 minuets in bed, get up and go do something boring until you get sleepy and try again.

Don't do any other activities in bed, other than sleeping, and one other thing ;)

Use the light and dark, basically go to sleep when it's dark and wake up when it's light.

Create a routine and stick to it, set a waking time and do it every day, Monday to Sunday. You will go to bed at different times, but wake up at the same time. That way your body will make you sleepy when it's actually time to go.

Don't drink caffeinated drinks later than say 3pm

Exercise.