I think there are a lot of people who use lucid dreams for practical purposes already, so there's not much need to elaborate on it. Part of the International Space Station was designed by an engineer in his lucid dreams. Also, some musicians rehearse their songs in lucid dreams, and martial artists practice sparring techniques in lucid dreams.

Personally, I like to use them to meditate, mixing my mind on deeper and deeper levels with beneficial ways of seeing the world so that when I'm awake, it's easier and more natural to respond constructively to whatever happens.

I know someone who deeply looked into the meaning of life in his lucid dreams. But he has them all the time any time he wants. I haven't been that lucky so far. He says that for him, it's simply a matter of wanting to have lucid dreams, and he'll have them - no special techniques. I remember him telling me that at one point it got a bit too intense, so he stopped it and just has regular dreams now. I don't understand why anyone would stop them personally; I'd be awake forever if I could.