It has been a LONG time since I read Castaneda, but as a first step, he stressed executing a simple command, specifically, looking at your hands. As a second step, he emphasized identifying an anomalous object in a dream, focusing on it, and then transitioning to a new dream while retaining lucidity.
I do not want this to seem like I am endorsing Castaneda. There were a lot of things about him that were very sketchy.
Castaneda's descriptions of further steps in lucid dreaming get VERY far out, and it is far from clear that what he was describing corresponded either to his actual experiences or to what is the actual potential as lucid dreaming as some kind of tool.
For me, lucidly dreaming regularly came about from what you mentioned already: regular reminders throughout the day by asking, "Am I dreaming?"
I do not pursue lucid dreaming at the moment.
RE: How Shadow People From My Dreams Taught Me The Power of Fear and Improved My Writing