When you first lay down to go to bed, relax your entire body and try to calm down your mind.
Meditation can be an effective tool for this and great and calming you.
Also, I'm sure you've heard of techniques that help you go to sleep, such as counting sheep, but I learned a different one recently that has been awesome:

Imagine you are standing in front of a chalk board. Draw a circle and write the number 99 in it. Then write the word "Deeper" next to the circle. Everytime you write the word deeper, feel yourself falling deeper and deeper asleep.
Erase the number 99 and be careful not to erase the circle. Write 98 and then write Deeper. Repeat as long as necessary.
Try to do this slowly and stay focused with it. Once your mind realizes that you are determined to do this as long as it takes, it will not want to waste more energy doing it and will turn off.
I hope this helps! Good luck going to sleep!!