The "1,2,3" rule is simply reading the first sentence of text out loud 3 times before going into the rest of it. Supposedly, by the third pass of the first sentence, your brain has tuned into where it needs to be and the rest of the performance will go a lot smoother. After learning that from a coach and implementing it into my auditioning, I noticed that they were sounding much more polished, even after just a single take.