The Christian Science Monitor was nice enough to put together this Draft Refresher Course to help us all get ramped up on the logistics of sending an entire generation to their deaths:

A lottery based on birthdays determines the order in which registered men are called up by Selective Service. The first to be called, in a sequence determined by the lottery, will be men whose 20th birthday falls during that year, followed, if needed, by those aged 21, 22, 23, 24 and 25. 18-year-olds and those turning 19 would probably not be drafted…
…According to current plans, Selective Service must deliver the first inductees to the military within 193 days from the onset of a crisis.

Here is the full text of the article in case the link goes bad:
http://www.csmonitor.com/explainers/Draft.html
Questions and answers about…
The Draft
Overview:
While there have been no formal, public proposals for a reinstatement of the draft, the national campaign against terrorism has turned America’s thoughts toward issues of military preparedness.
But according to Jeffrey Taliaferro, an assistant professor of history at Tufts University, “Any reinstitution of the draft would be extremely unlikely, even in the aftermath of [the Sept. 11] attacks.”
“The primary opposition to a reinstatement of the draft would most likely come from the armed forces themselves. Reinstating the draft would require the military to divert additional resources (Non-Commissioned Officers, money, building materials, etc.) from frontline and reserve units. In any given pool of inductees, there would be a number of men who seek to avoid military service, but failed to obtain ‘conscientious objector’ status. In addition, there would likely be inductees of sub-par educational backgrounds.”
1) What happens in a draft?
The following overview is taken from The Selective Service System’s web page.
A. Congress and the president authorize a draft
A crisis occurs which requires more troops than the volunteer military can supply. Congress passes and the President signs legislation which starts a draft.
B. The lottery
A lottery based on birthdays determines the order in which registered men are called up by Selective Service. The first to be called, in a sequence determined by the lottery, will be men whose 20th birthday falls during that year, followed, if needed, by those aged 21, 22, 23, 24 and 25. 18-year-olds and those turning 19 would probably not be drafted.
C. All parts of selective service are activated
The Agency activates and orders its State Directors and Reserve Forces Officers to report for duty.
D. Physical, mental, and moral evaluation of registrants
Registrants with low lottery numbers are ordered to report for a physical, mental, and moral evaluation at a Military Entrance Processing Station to determine whether they are fit for military service. Once he is notified of the results of the evaluation, a registrant will be given 10 days to file a claim for exemption, postponement, or deferment.
E. Local and appeal boards activated and induction notices sent
Local and Appeal Boards will process registrant claims. Those who pass the military evaluation will receive induction orders. An inductee will have 10 days to report to a local Military Entrance Processing Station for induction.
F. First draftees are inducted
According to current plans, Selective Service must deliver the first inductees to the military within 193 days from the onset of a crisis.
2) Will gay men be screened out of the military by the draft?
Lew Brodsky, Director of Public & Congressional Affairs for the Selective Service System, says the main emphasis of the Selective Service’s moral screening process is exploring a potential draftee’s legal history, not preventing homosexual men from being inducted.
“The ‘moral’ portion of determining a man’s suitability for military service is a police check to see if a prospective inductee has a felony record,” says Brodsky.
Professor Taliaferro agrees: The draft’s main emphasis isn’t on screening out suspected gay men.
“Under the Defense Department’s pathological personnel policy (a.k.a., Don’t ask, Don’t tell), recruiting officers are not allowed to ask would-be recruits about their sexual orientation,” writes Taliaferro. “If the would-be recruit volunteers that information, however, he or she can be excluded from military service.”
“I would imagine that if the draft were reinstated, the current exclusion policy would remain in effect. Whether local draft boards would uniformly comply with directives to screen out gays is a matter of speculation. This, of course, raises several additional problems and paradoxes:
“(1) Presumably, troop shortages would be the main rationale for reinstating the draft. If the armed forces are unable to main sufficient troop levels during the current national emergency, it would seem rather absurd (at least in the minds of most educated, middle-class or upper-middle-class Americans living outside of the deep South and the heartland) to systemically exclude young men from military service based upon sexual orientation. Opponents of the draft in both the House and the Senate would likely raise this issue in committee and floor debate on legislation to amend the Selective Service Act.
“(2) The systematic exclusion of any discrete group of young men from mandatory military service would undermine the Bush administration’s rhetoric about American unity.
“(3) A sizable number of 18-26 year-old men would tell their local draft boards that they are gay in an effort to avoid induction.”
Why aren’t women required to register?
As it is currently written, Selective Service law refers to “male persons” in stating who must register and who would be drafted. A Supreme Court decision written in 1981 (Rostker v. Goldberg) held that registering only men did not violate the due process clause of the Constitution.
An extensive history of women and the draft is available on the Selective Service System’s website.
Who serves on draft boards, and how many are there?
“There are about 2,000 Local and District Appeal Boards composed of 10,600 uncompensated civilian volunteers,” says Brodsky. “Each board member is nominated by his/her state’s governor and appointed by the Director of Selective Service on behalf of the president.”
The goal is to have Board Members that makeup of the communities they would serve. Board Members are both men and women. They cannot be retired or active military, nor can they be serving in the National Guard or Reserve. Additionally, they cannot be judicial or law enforcement officials.”