I have managed to get my reputation up to VERY Trustworthy with:

As sed abowe:
-always Occupaying settlement (eaven Rebels)
-always releasing prisoners

But i also:
-only siegen settlement never attacked them, only defending the sige
-having 3 alies who were also alies betwen them
-my stands with them was ALWAYS at least Outstanding

AND WHEN I NOTICED THE BEST INCRESE WAS WHEN I FOUGHT BATTLES WITH MY ALIES TOGETHER!!
I did it like that, when my alies enemy (not mine until then) lets say sieged my alies province (city, castle) i standed my army close to the city and when they attacked from the siege my troops automaticaly engaged in battle ,so i auto declared war and my reputation INCREASED :)
It also works when you bring your troops and attack them while they are laying siege, then your alies will help you defend them, rep. also increases