I am going to just give you everything that I know and have learned. Hope this helps!
You need figure out what classification you are in (1c,2c, 3c....) and that will decide how much time you get in your general and summary period. I am 1C so I get 4 min for general and 3 for summary period.
During general, address the key/accidentals, stick to 1-2-3-4 and telling the kids who plays when. It really helps them know if they are playing by themselves, if it is just brass or just woodwinds, have the melody, or not important parts...(Dynamics and style should be mentioned here too) If there are fermata's or tempo changes, you should also address how you will do that here.
During summary, You can literally count the rhythm for them. So focus on parts that kids will get stuck on or that you know will be challenging for them.
Add the stuff that you did with the general to give the kids a sense of repetition and you should be good to go!
I would practice sight reading with the kids at much as possible to put yourself and them at ease. Make sure the kids all look good/same at fingering! This will show the judges you know what you are talking about and have taught them well!
At some point, you have to learn to trust that your teaching has worked.
*Other directors let me know if I need to change or add other things to this list.