If you can't sleep, you can't sleep I've found sometimes you just have to sit there and wait for sleep to come. Sometimes I sit in bed awake all night and its better than staying up, because I'm still more rested than if I had ran around all night... Haha I probably didn't help you at all but yeah
Pay attention to you eat or drink in the evening. Tea, soda, chocolate all have sugar and normally caffeine too. That will keep you awake. If I go out to dinner, I ALWAYS drink water or I will have the same problem. Sometimes a hot bath and a bowl of cereal (no sweet cereal) can help you wind down to sleep. Music and TV will keep me awake.