Here is my little kit for efficient instrument work!

PEN, ETC.
A pencil and a good eraser for annotating;
A black pen, preferably ball point, and a white-out tape to clarify changes in general indications, such as pedals changes;
Highlighters, for important things

A NAIL CUTTER
Always important to have on hand

CANDLE
To feel relaxed

METRONOME
The real good old version, with a loud sound

TUNING KEY
To be gentle with your neighbors' ears

NOTEPAD
To write down all the ideas that cross your mind and challenge your concentration

TEA AND NUTS
Any type of drink and snack of your choice that won't get your fingers dirty, to maintain your energy level

Enjoy your practice time!