I have massive sympathy for the OP - I had awful insomnia for nearly a year when I was at uni.
As others have said, there's usually an underlying worry that is responsible. Whatever it is, it stops your brain winding down at night and all the time the brain is active, you're stuffed. Anything else that keeps your brain active late into the evening is best avoided, and if you can physically exhaust yourself alongside allowing your brain to wind down, you will make progress.
Alcohol works to a limited extent because it dulls the brain, but obviously it's not a healthy solution. Getting laid works because of the hormones released as a byproduct which have a soporific effect. Other little details, like making sure you have the right mattress and the temperature in your bedroom is suited to you, can help too, but not to as much of an extent.
Ultimately, the solution for you will be a personal one, because it needs to address the individual cause that is affecting you. My problem was that I was pretty depressed and when I managed to start addressing my depression I became less worried about it, which in turn meant I started to sleep a bit better. One very strange step that helped me was not sleeping alone - I had an amazingly supportive female friend at uni who listened, understood that it wasn't a sexual thing at all and was prepared to share a bed with me fairly regularly - although inviting her to my wedding has somewhat upset Mrs. Tree lol! Another thing that I found helpful was going to the local RSPCA kennels and taking out some of their dogs every week for a decent walk - combination of fresh air and unconditional love worked wonders.
Whatever is keeping your brain active, work on that. The sleep will sort itself out as a result.