Note that most of my advice is geared towards medium sized kingdoms.
1. Keep council members of your strongest vassals. They will not be able to faction, so long as the council is content.
2. Pay attention to the vote tool tips. You can often find out why this Councillor votes for or against an action and fix it.
3. The wiki has a great bit on why the AI picks a certain stance. Pay attention to your potential Councillors traits and make sure they have a high opinion of you before you place them on the council.
4. Unless you really need to lock up another vassal, keep the Advisor(s) spot for someone guaranteed to be loyalist (friend, lover, close family member, high opinion content vassal) to use as voting leverage, sparing you from giving out too many favors.
For some numbers:
1. Council members will usually support increasing centralization at +20 opinion. They will always support reducing centralization.
2. Revocation will almost always be voted down at an opinion below +60, above +60 turns voting assumption to undecided. Special rules for zealots (will vote for stripping titles of religious enemies) and pragmatists (will vote yes with opinion above +20)
3. Most voters will be opposed to any increase in laws concerning inheritance, vice-royalties, and administration.
4. Feudal councilors will be opposed to increasing their levy obligations, mayors will be opposed to increasing their tax obligations, and bishops will be opposed to any change from a balanced obligation. Councilors will be undecided on obligations that do not affect their own government type.
There is a lot more to it, all listed on the wiki. Worth checking out.