Practice, Practice, Practice.
I use Spray paint or duct tape to mark the depth needed. I measure from the teeth.
Be careful swinging the boom side to side. Some backhoe models allow the boom to hit the outriggers, or step.
On some models bending the boom in a hard swing by hitting the trench side or stump is not unheard of.
Something else you may not notice right away; the swing control is ALSO proportional/progressive, i.e. you don't have to idle the tractor right down to avoid violent swings that are so uncomfortable when the boom and dipper are extended.
Just develop the feather touch to accelerate and slow the swing gradually.
It barely costs you a few minutes on a day's work to swing gentle, but it is so much less tiring.