First, that the group represented is as small as practically possible, so small numbers of people, small cultural subgroups, and a limited social distance between the elected official and the constituents.
Second, that the rules governing a group are as local as possible, large disagreements should be unusual, and ideally lead to splits in region. Issues on a state or federal level should be limited to interactions with other states or nations; weather or not you want to live in a group with legal abortion for example should be determined at the the smallest size that can make that decision; probably city by city, what people in other cities think should have no bearing.
Unfortunately the nature of government is to centralize and accumulate powers, things that were once the sole preview of a town or county are now federal issues. It seems impossible find a "fair" voting method, to reconcile how to weight two distant strangers opinion on what should be a local matter.