Here are three other things I thought of.

1. Don't watch TV or computer late in the evening. The light from tubes of any kind is very intense, and it wakes your brain up just when it ought to be going to sleep.

Watch TV with your eyes closed sometime. It is amazing the number of brilliant flashes of light you will sense right through your eyelids. That gives a sense of what it is doing to you.

Better yet, watch one from the back. It's like a small lightning storm.

2. Many people (maybe all people) are kept awake by alcohol. Yes, it may make you sleepy at first, but five hours later you can be stark, staring awake. One beer or glass of wine can do it.

3. Make your bedroom nice and dark. Block-out shades, for example.

My sister used to have an apartment with big windows in it. One day she came to visit and slept in my room - block-out shades, closed door to the hall, and dark brown wallpaper. In the morning she said, "That is the best sleep I have had in a year."