I agree that the system isn't very well designed. It's a nice feature in general but they should have put it at least twice the work they did.

What I always do is get as many allies as possible, which will nicely normalise your global standing towards 1 (while it also normalises towards 0 twice as fast, which means you'll reach an equilibrium at 0.33 if you have one ally - being at war with a non-rebel faction normalises towards -1 with half the speed of the ally normalisation).
Releasing more than 80 prisoners gives 1/40 on top of the usual 1/100 as does releasing a character, if you do both you get 1/20. You also get that figure for occupying a settlement - rebel or not. Executing rebels will give you -1/20 even if you may not notice it immediately.

A good global standing will help your faction standing with everyone, not the other way around. This can almost make up for the normalization towards -1 you get on vh so is a powerful thing.
Breaking treaties or alliances can give you a big hit, so be careful who you ally to (make it so you don't ally to a lot of factions who're likely to declare war on each other)

All these are taken from vanilla 1.2