For me and most of my clients I've found the best way is via Google AdWords. Yes, I know you've probably tried it and it hasn't worked. But that doesn't mean it doesn't work. It means the way you did it didn't work.
The problem with AdWords is it looks so simple...it must be easy. It is simple. It just isn't easy, to do well, that is.
But I already know this. How about you?