There are two basic types of revolts: Revolt by the leadership or other small group, and revolt by the general populace. You can't really do anything about the latter except be prepared to gas them all and re-settle the area with your own people and you did ask specifically about regional governors, so I'll focus there.
A local ruler who wishes to revolt against the empire needs a few, basic things. He needs to get the bureaucracy on his side so they won't rat him out or desert him. He needs a sufficient stockpile of defensive resources to prevent the empire from simply conquering the area again. He needs to get the people on his side so they don't simply refuse to support him and switch to following whoever the emperor tells them to next.
All of these resources take time, planning, and personal charisma to acquire.
Assuming you're thinking the "evil empire" bit, denying the regional governors the opportunity to gather the needed resources is fairly straightforward. Appoint the governors to fairly short terms, probably a year, two at most. This limits their ability to sway people to their cause. Further, select governors by random lot from the general population of the entire empire. This makes it pointless for anyone to try to build a base of followers and then get an appointment, because the odds are millions to one against.
Appointees are taken in the dead of night and installed in the governor's mansion. If they serve well and faithfully they are returned home at the end of their term and given a small-but-useful pension. If they're not competent they simply disappear and are never heard from again and a new governor is appointed. If they prove actively traitorous they and all their family, friends, and anyone who is known to have had more than one conversation with them gets executed.
Service is mandatory. Any who refuse or complain are treated as traitors.
Put it together with a healthy incentive program whereby anyone who unmasks a traitor gets a small-but-useful pension and you can probably keep it going for quite a while, as long as you don't mind a fairly high rate of executions and being constantly surrounded by idiots (until you disappear them and select another, random replacement anyway.)
Just make sure you keep the locals believing that you're honestly doing your best and that it's really the provincial government that's invariably corrupt and the source of all their problems. That way they'll never turn on you.