2. Sticky notes/flags. You cannot mark on the score, but you CAN place post-its on it. I use colored flags pointing to accidentals, solo/soli lines, and entrances as I go through it.
3. Make 100% sure you communicate with the host school as to what IS and IS NOT being provided both on stage and in the SR room for percussion. If you're reading a piece that calls for triangle, tambourine, and bells, and they aren't providing those, you need to make a kid responsible for bringing each. (Your stage selections in theory will use those common instruments, but I've done a UIL concert or two where I didn't use an instrument that was needed in the SR room).