Coincidently we just went to a 4 H fitting and showing clinic this past weekend. We've been showing for 5 years now.
I would definitely watch some videos. You can find some on you tube.
Go to ADGA's website. I know they did a live stream of the national show last year, I'm not sure if they recorded though.
I've showed junior dry yearlings who were already bred, but no reason to show a senior not in milk.
Most important thing to remember is you can wear whatever color clothes you want as long as they are white

Some judges say it's OK to wear black pants but better to stick with white in case the judge you are showing under is a purist.
Never be between the judge and the goat. When you switch sides always cross in the front.
Use show collars.
Know your goats strengths and weaknesses show to her strengths and try to cover her weaknesses. You can mask weakness when you set them up, but hard to cover a weakness when they are moving.
Do not show goats if you will be upset if your goat comes in last place. I've had a goat win a Jr Championship in one ring, and come in last in her age group in another. I have a first freshener we showed 4 times last year. She won her age group 3 times one of which she took Reserve Grand Champion. the other show she came in dead last.
Don't take it too seriously and have fun. It is a wholesome, fun family activity for us.