To help children get settled for sleep have a consistent bedtime routine. An example would be put toys away, eat tea, clean up dishes, bath or shower, toilet visit, clean teeth, listen to story. Older children can read in bed or listen to their music.
Some children become more excitable rather than calming down with a story. You could sing with them instead.
Still having problems getting to sleep? Encourage the child to stay in bed except for a toilet visit. You could play a taped story or relaxing music. A night light may help. Visualisation exercise - imagine you are playing your favourite sport and you are the star of the game.
We all have occasional night when we can't sleep but for some it is an ongoing problem. If it continues for too long have a chat with your doctor.
If you have some ideas that have helped a poor sleeper please help another parent by adding them here.