Some things they have told me is: Don't eat before bed, take a cup of tea right before bed to soothe you. Soft music does help immensely.

Personally, I have taught myself to recognize that I am dreaming, as I am dreaming it. This works about 90% of the time, because when you realize that you are having a nightmare when having the nightmare, it takes the fear out of it quite a bit, like watching a movie almost. You do have to deal with your waking thoughts, "Why do I have such horrible things in my head". However, this takes alot of time and work. Also, when one makes you believe what you are dreaming its almost worse somehow. They really get you. I know I am not much help, but I have horrible nightmares often too.