There are all sorts of scenarios for an orderly exit from Iraq. The best one I can devise is this:
1. Withdraw American troops to bases, and get involved on the ground only when the Iraqi government requests it. Put reconstruction completely under Iraqi control, and minimize involvement of American contractors.
2. Work through the UN to broker a cease fire between the insurgents and the Iraqi government. As heinous as the acts of some of the insurgents are, they are doing the same thing the US Government is doing, on one level: pursuing political goals by means of military force. They have the support of a significant percentage of the Iraqi population, and until those people have a real political stake in peace, they'll continue to support the insurgency. Given that their primary policy goal is that the US Military get the fuck out, the US and the Insurgency have at least one common goal.
3. Get regional Arab governments involved, to send peace keeping troops. For all the talk of Arab unity, Arab governments are all too willing to let the Iraqis twist in the wind until some legitimate moral authority demads their positive involvement in solving Iraq's crisis.
4. Withdraw as soon as the government is reasonably stable, and peacekeepers are in place.
The problem I see now is that the Iraq war is in about the same place as Vietnam in 1968:
1. We're going to leave without winning any clearcut victory; the only thing certain is that the number of Americans killed, and the number of Iraqis that American soldiers kill, will be a function of how long we decide to stay.
2. Unless there's a strong international effort to help a democratic government become stable and in control of Iraq, the existing government will be gone not long after we leave Iraq.
Bush's bungling of the war and it's aftermath, and debacles like Abu Ghraib gives the US zero moral authority to dictate how things will go. I was going to give
Einstein's definition of Insanity here to describe Bush's actions in the past two years, but after googling it I realize that however apt, it's a cliche. Bush thinks, apparently, that he can kill enough Iraqis to turn Iraq into a Western-Style Democracy. This strategy has never worked.