Here are some helpful tips from students who have made the last round of All-State in the past:

They practice sight-reading.
They practice daily for about 45 minutes or more for a few years before they are able to make the second round.
They are very good sight-readers. They use sightreadingfactory.com or practicesightrheading.com regularly.
They practice sight-reading.
They practice slowly and with a metronome.
The student is able to play the excerpts on first sight at half tempo with very few mistakes.
They practice sight-reading :)
Sometimes it makes sense to wait a year or so before we try for All-State so we can learn techniques and reading necessary to prepare for All-State.
Sight reading practice is 80% of what gets you through the second round.
Did I mention how important sight-reading is?