Not a professional but some tidbits picked up over the years:
Grass has to be in the growth mode to grow so if you have signs of end of life of a plant, aka seed heads, mow/graze it which will put it back in the growth mode. Forage is more digestible and nutritional in the growth mode also.
Stubble has to be tall enough to contain enough "sugars" to activate/supply regrowth until enough leaf emerges for sustainment.
Pasture rotation is essential for productive pastures for the reasons listed above. Amazing what can be grown off properly rotated pastures vs non rotated, free choice, non controlled grazing.
My rule of thumb is once good growth is established, height depends on plant, turn them in on it. When they graze (stomp) it down to 6" for a conservative number, take them off and let it recover. Feed out the hay in a separate area but accessible from the active growth field.
Heavily fertilized, active growing plants for stand alone grazing without dry matter can lead to problems (an observation from other's mistakes).
When turning into a new, freshly grown pasture, ensure they have been fed first, and not turned in hungry.
Be aware of the hazards of your particular type of grazing plants and be alert for problems before they become a problem.