As a very bad sleeper I have read an awful lot about the subject and actually remembered a bit of it.
One of the most useful items in a serious aviation journal, written by a doctor, said that one sure way NOT to get to sleep, especially in the afternoons prior to a night flight, is to start worrying and getting agitated about not sleeping. Opinions will differ but, lying in a darkened and quiet room, (ear-plugs and eye-shades if you have to), relaxing and not worrying whether you sleep or not can be between 60% and 70% as good for you as sleeping.
Regarding exercise I was told not within 3 hours of going to bed as your systems are still on a 'high', it didn't classify a good 'bonk' but I believe them to be very theraputic myself!