Intonation: Bar Control
One simple thing to ensure you do is keep the bar straight (unless you are compensating or slanting), this is easily overlooked and needs to be second nature.
Developing strength and detexterity in your left hand will also help as it will allow you to make micro-adjustments to the pitch, these adjustments work in parallel with what
you are doing with your left arm.
It will also enable you to hold your bar in a variety of different ways which will improve your stamina, and allow you adjust the way you hold the bar as your arm moves up and
down the neck causing the position of your hand to vary.
On recommendation again from Joe Wright, I have begun wearing weights on my left(bar) arm when I’m practising to accelerate development of vibrato and fret accuracy!
Intonation by eye and ear are skills to practise independently.
In your playing these two approaches have their own roles, typically you will move the bar by eye to the approximate place and then adjust by ear, the two skills will complement each other.