Change one thing at a time
Keep dose and yield stable while you adjust grind size. Otherwise you will not know what changed the shot.
Make small grinder changes and taste before moving again. Espresso rewards patience.
Fast shots
If the shot gushes through and tastes thin or sour, grind a little finer. Check that the coffee bed is even and that the basket is not underfilled.
Do not fix every fast shot with more coffee. Start with grind and puck prep.
Slow shots
If the shot chokes, drips slowly or tastes harsh, grind a touch coarser. Also check that you did not overdose the basket.
A slow shot can still taste good, so use taste as the final judge.
A simple routine
Write down dose, yield and time for a few shots. You will quickly see patterns.
Once the shot tastes balanced, stop adjusting and enjoy the coffee.