Dreaming, in castanedianism, is a technique for being aware and act purposefully while asleep. Extending awareness into sleep! Dreaming is considered to be 'real'. It is one of two roads for a practitioner, the other being stalking. Remember that all sorcerers do both dreaming and stalking, but that a practitioner often have an affinity for one of them. I believe that being 'introvert' or 'extrovert' has little to do with ones predilection.

To be aware in dreams is often referred to as 'lucid dreaming'.

The technique of dreaming is described in detail in 'Art of Dreaming' [cc9], but dreaming is also described in 'The Eagles Gift' [cc6]. The events in 'Art of Dreaming', the ten first chapters, comes chronologically before the dreaming events under the tutelage of Zuleica described in 'The Eagles Gift'. The events from the later chapters in 'Art of Dreaming' are from the last year of Castanedas apprenticeship.

The procedures of dreamers are as follows:
-First, to free energy by living like a practitioner.
-Second, to develop the energy body, also called the 'dreaming body' or the second self.
-Third, to use awareness as an element of reality to enter into other worlds with our total being.
 

References from Castanedas books:
Journey to Ixtlan [cc3]: ch 10 (first mention)
Tales of Power [cc4]: ch 1, ch 'Having to Believe'
Second Ring of Power [cc5]: ch 'Art of Dreaming'
The Eagles Gift [cc6]: part 2, part three
The Fire from Within [cc7]: Various parts...
The Power of Silence [cc8]: Beginning of part 2 'The Abstract' and part 4 'Seeing the Spirit'
The Art of Dreaming [cc9]: Whole book, more or less.