I don't go in trying for lucidity. Usually I've woken up before the dream accomplished whatever goal it had and I go back in and get it done by focusing on what I was doing and who I was with. I haven't been able to completely control a dream, but I've been aware I'm dreaming and that I need to do something and have attempted to complete the task.
The subjects are obviously pleasant. Things like memories from childhood, solving a mystery, women, dying, etc.