Skip Youtube and go straight to the source for some good video!
http://www.westminsterkennelclub.org/videos/Breed Judging/2013/Herding/vid:2624785
That link should take you directly to breed judging for ACDs.
Keep in mind that not everyone you see will be a great handler. The people you don't want to emulate are the ones that can't. stop. touching. their. dogs. Constantly adjusting your dog just tells the judge "Heeeey look at this! There's something wrong here and I keep fixing it!" Really good handlers make the dog look like it's showing itself. They're the people that make everyone think that "showing dogs is easy."
I have consistently battled anxiety and CRAZY ring nerves over showing my guy, so I will give you some advice that has helped me.
The most important thing of all is to SLOW DOWN. Your immediate compulsion when you get in, is to go like a bat out of hell. You're going to feel this desire to do everything fast because there's people waiting behind you, or the judge is staring, etc. Don't fall victim to it. Just breathe deeply, and move smoothly. Smile at your dog. If she already knows how to free-stack, go with that this first time around, so you don't feel pressured to set her up perfectly without a lot of practice.
When you move her, be sure to ease into the preferred speed (whatever movement SHE looks best at) for a few steps. Giving her a slow build up into that pace just looks better, and also lets the dog know what to expect.
Good luck! Honestly, as nervous as I get, it is still addictive. The minute I walk out of the ring I am already excited about doing again (even if I spent the past week being nervous!) I am sure you will have a great time.