I have this problem too. So far, I haven't been able to find an answer to that problem. sometimes i try to concentrate only on one thing. But it is very hard to do it properly. Our mind tends to go here and there very often. other thing that I have tried out is listening to music. It works more often than not.
Umm well if there are nights when I can't fall asleep coz I'm not tired, I read a book and eventually fall asleep but if that doesn't work, close ur eyes and in ur mind draw a circle and right 100 in it, then next to it write "deeper and deeper", then rub out the 100 and write 99 and go over the deeper and deeper. Keep doing that until you fall asleep that really helped me. Also u can close ur eyes and COMPLETELEY relax and imagine your absolute perfect place imagine every little detail,and imagine urself there eventually ull fall asleep! Good luck and I hoped this helped :)
Take melatonin. It works within 30 minuets of having taken it. Also, try a few different herbal sleepy time teas. Those work AMAZING! :D I know, because if I don't take sleeping pills, I'm awake until 3 a.m.