1. Voting shall be a privilege reserved for adults over 25 who pay tax. Military service also shall qualify a citizen to vote.
2. Taxation shall be the same for every citizen, $10,000 or less per year, and shall only be paid by non-military voters. The only sanction for non-payment shall be omission from the published list of voters. Government shall shrink as necessary to fit this taxation and taxation shall shrink as necessary to fit this government. Unless agreed by taxpayer referenda requiring a super majority to be renewed each year, there shall be no other tax except tax hypothecated for emergencies. Tax from each taxpayer shall be divided equally between each state and the United States.
3. Elected representatives shall serve for the honour of public service, but not for pay, and shall be subject to term limits at the federal level.
4. Preferences on any grounds or none shall be legal in the private sphere, but illegal in the public sphere.
5. There shall be no public health service, but no child or military veteran shall be denied medical assistance for want of funds.
6. Marriage shall be a wholly private institution. There shall be no legal implication other than the overriding social interest to protect children. Spouses or anyone else may use the law of contract to define any material aspects they wish.
If your first reaction is 'how simplistic', think how the Framers would react to what we have now. Imagine the liberating effect on private enterprise, private charity, civic equality and civic pride.
Update: Barbarian Barney Frank provokes this apt quote from Robert Heinlein in The Corner-
The America of my time line is a laboratory example of what can happen to democracies, what has eventually happened to all perfect democracies throughout all histories. A perfect democracy, a "warm body" democracy in which every adult may vote and all votes count equally, has no internal feedback for self-correction.... [O]nce a state extends the franchise to every warm body, be he producer or parasite, that day marks the beginning of the end of the state. For when the plebs discover that they can vote themselves bread and circuses without limit and that the productive members of the body politic cannot stop them, they will do so, until the state bleeds to death, or in its weakened condition the state succumbs to an invader — the barbarians enter Rome.