I've always been an insomniac... Not quite full fledged all the time, but I did have a full blown disorder for a year or two. Besides that, never slept well even as a baby (the stories my parents tell... egad).
It really comes down to why you can't sleep. If it is just behavioural, you can train yourself out of it really quickly. However, if it's a mix, or just biological, nothing you do will matter at all. You will literally take things that should knock you out... but they'll just make you drowsy - ie: drugged. If that's the case, you'll be stuck getting some very powerful things that practically induce sleep... and you have a very high chance getting addicted to them.
In any case, the three things I can suggest;
1) Use your bed for sleep. Nothing else but sleeping. When you go to bed, if you can't fall asleep within x time (normally from 10-30min), you get up and do something tedious. You don't read or anything similar. Nothing that engages your mind. And to emphasise this one more time - do not do anything else in bed - no reading, no napping, no watching TV... maybe sex, but that's about it.
2) Excersize, but give time before you go to bed - more than 2 hours. This works because stress and an active mind are bad news for sleeping, but the excersize does cause your body to wind down - after the high. It shouldn't be intensive, a good 30 minute walk or anything similar can be enough.
3) Create a routine for going to bed. This works well with #1, so it should start with or after you have made your bed your sleep area. Always do the same things in the same order for 10-15 minutes before going to sleep. Try very very hard not to interrupt this.
There was other stuff that the sleep clinic suggested, but I remember these as the core ones.