Once center is found, then one must strive to include others and show respect for the opposed principle. It is a mean between two extremes - more just and stable. Practical rules of thumb are - democrats should spare rich, oligarchs should help the poor. Also seek to combine compementary rules, or take the mean of rules, or mix up rules for votes, for office qualification etc. IV.7 e.g., fine rich, but pay poor for attending court.
Law makes for moderation and fairness.
Consider, yes, term limits - so that tyrants cannot emerge. Watch social customs that contradict regime principle. Aristotle elaborates on many practical devices. The citizens need good habits and good teaching. The citizens need at least a citizen virtue whereby the regime is perpetuated.