It depends on the cause of your insomnia. Do you have any ailments such as arthritis? Are you on any medications that could keep you awake at night?
If there are no extenuating circumstances, melatonin is the natural chemical our bodies produce to make us sleepy and this is sold over the counter and is very safe if you are uncomfortable asking your physician for something such as Lunesta. A lot of people are uncomfortable taking prescribed sleep aids because some of them are addictive and then your body ends up relying on it in order to go to sleep.
There are also of course stress related issues that could cause insomnia. If you have something troubling you it may be beneficial to talk with someone to get it off your chest.
Lastly but not least, what comes to my mind, is eating before bedtime. You don't want to load up with a lot of sugar before bed. Another natural remedy is sleepytime tea.. it works great!
Good luck to you