When I have trouble sleeping at night I will take a 30 minute walk around town and then by the time I get back to my house I'm usually tired enough that I fall right asleep.
There's something about walking that helps you to get to sleep.
However sometimes that doesn't even work and I then drink some warm milk.
Warm milk is a natural sleep aid that for some reason puts people to sleep after drinking it.
Also try going to bed at the same time each night and keep electronics out of your bedroom and reading a book can also help some people sleep.
If none of that works then you may need to try some over the counter sleep aids as a last resort.