Something like counting sheep - but in reverse.

1. Count down from 100 to 0
2. Imagine each number ( like you are viewing in a calculator display or in any font you like )
3. External thoughts may come and go , consistently come back to the last number you have seen.

I usually wander in external thoughts for .5 or 1 sec and come back to the last number. Then, sleep somewhere between 50-30

4. For morning time / loud surroundings, use a White noise music. Low volume on a Noise cancellation earphone.