Cueing skills are developed by copying your past Yoga instructors, video tapes, and repeating the directions you have read in your texts. Once you have finalized your lesson plan, try it out on a friend. Practicing your cueing technique will develop your skills.
If you want to critique yourself objectively, run a tape recorder and teach a mock lesson. When you play it back, you will see how your voice carries throughout the room. You can also follow along with the tape to see, if your directions are easy to understand. This type of an exercise will fine tune your ability to teach a Yoga class, as you learn to overcome any weak points you find.