Flex those muscles: Relaxing your muscles is a great way to trigger sleep. Start by moving your toes, and then work your way up, focussing on flexing muscles in each part of your body. When you get to your core (stomach), indulge in some deep breathing.
Take a shower: Water can ease built-up stress in the body. A hot water bath before sleeping will relax you.
Cuddle up: Spend some time cuddling your partner, just before you go to bed. This activity stimulates emotions that are, by nature, soothing.