Hi Carmen
Congrats on becoming a BS instructor, the best programme LMI offer!!!
For video certification, it really depends on where you are not sure about the US but here in Australia, you are expected to know your chorrey, 100% is great however in saying that if you make a mistake you won't fail, as long as you get back on track within 8 counts it might even be 16 counts. On a 3 strikes your out basis. So don't worry. They look for strong arm lines, and depth in your squats, track 5 particularly. Don't forget to throw in safety tips, knees track your toes, body alignment etc.
As for previewing moves, where ever practical do use it, shows you know your chorrey (if you aren't sure of the chorrey you're not going to preview, right?). Oh yeah, throw in a person's name or two, doesn't matter if they are in the class or not. Shows you have connected with your class.
Smile alot and enjoy show your enthusiasm!!! Good Luck! Let us know how you go!
Happy Stepping!!
Always Be the Best You Can, Never Ever, Ever Give Up! Dare to be Different! What You See is What You Get!