Here are the big four...
- Do you have a resonant, centered tone in different registers?
- Can you play in tune with yourself and others?
- Can you hear the notes in your head before you play them?
- Can you keep a steady tempo?
- Can you subdivide correctly within that tempo?
- Can you begin the notes cleanly?
- Can you control all these elements as you play.. high and low? ...loud and soft? ...fast and slow?
- Do you know exactly what the piece should sound like?
- Do you know where you are going to breathe?
- Do you know where to crescendo? ...whether to use vibrato? ...how much accent to use?
- Do you know exactly what slide positions you're going to use?
- Have you heard multiple recordings of the piece?
- If a solo, do you know the piano part well?
- If an excerpt, do you know the piece as a whole?
- Do you know the meanings of all the terms?
- Can you close your eyes and hear the precise sound of someone really "nailing it?"
- Are you aware when tension builds in your body?
- Is your posture well-balanced?
- Is your playing a natural extension of relaxed breathing?
- Is your tongue relaxed? Your throat? Your shoulders?
- Are you so focused on the music that you don't notice what is going on around you?
- Have you quieted any "inner conversations" about your playing, good or bad?
- Are you " in the moment?"
- Do you "disappear into the music" as you play?
I'm sure I missed a few but this seems to be a pretty good list.
Back to ye old performance equation...
P - I = R
Potential minus interference equals result.
Potential = (Fundamentals + Concept)
Interference = (Tension + Distraction)
Hope this checklist helps.