Serious question... does anyone here know how to make a lot of money?

I have been a student of the self-help genre for many years. Robert Kiyosaki, Anthony Robbins, David Allen (heard of him?), Robert Allen, Ken Roberts, etc. I've bought into different money making systems. Nothing has worked so far. I'm not blaming the gurus or their systems mind you. I am just explaining where I am coming from.

While doing a mind dump for GTD, I created a someday/maybe item for myself that says:

"Earn a full time salary through passive income."

Looking at that sentence now I realize it is a goal and not a project. That's okay. The important part is that I captured it in my trusted system. Now I need to process it.

I know this forum has a diverse crowd. I would like your opinion on how you would go about achieving this goal - breaking it down, defining it better, taking actions, whatever. If you already earn a full time salary from passive income, I really want to hear how you did it.

Thanks!