I didn't have insomnia as bad as some on the thread and with the caveat that every case of insomnia seems to be different enough that there isn't a single fix for it:

I found melatonin helped to get me started on a sleep schedule, but, in the long run, not as much as using f.lux and making my room as dark as possible at night. Got rid of my TV and listened to audiobooks instead.

I weaned myself off the melatonin supplements over a few months.

For the last two years I've been able to get a full night's sleep without much problem.