1. Popular vote:
No delegates. Period. The nominee should be the candidate who receives the most votes. Last time I checked, that's what democracy means. This also means that caucuses must be done away with. States can still choose to have open ballots; I think there's a good case to be made for doing away with the secret ballot, even if I'm not wholly convinced of it. But regardless, the caucuses would have to be like the New Mexico one, with ballots and tallies as opposed to caucus groups and viability thresholds.
2. No spoilers:
First past the post is stupid. It encourages tactical voting, and prevents smaller candidacies from gaining a foothold. It needs to be replaced. The most obvious choice would be instant-runoff, as that's actually in wide practice. My preference would be for the Schulze or Ranked Pairs methods, but anything from range to minimax would be much, much preferable to the current system.
3. Universal suffrage:
Democrats do a good job of this already by including Guam, the Virgin Islands, American Samoa, Puerto Rico, and D.C. Every voter within the United States, whether that voter is from a state, commonwealth, territory, or district, deserves a say in the nominating process. But "every voter" means "every voter". That is, every registered voter must be eligible to vote in the Democratic primary. Every primary must be an open primary. I appreciate the arguments of people like Trapper John who say that, as a private organization, Democrats have no obligation to include Independents and Republicans in the process. But the fact of the matter is that in a country with two viable parties, to have closed primaries is to disenfranchise millions of unaffiliated and third-party voters. They deserve a say, and they deserve more choices than "Obama or McCain" or "Kerry or Bush" or "Clinton or Dole". I'm more amenable to excluding registered Republicans from the process, due to things like Operation Chaos, but I also remember the week last fall before the deadline for party switching passed, as I and the rest of the Obama team called every Republican supporter and leaner we could think of and tried to get them to switch. Enfranchisement shouldn't have a deadline.
4. All at once:
This was the hardest part for me. Even as a New Hampshire native who got into politics because of the thrill of the 2000 Democratic primary here, I know it's impossible to justify two states having the disproportionate impact that we and Iowa do. But then again, Nevada showed the chaos that can result when states that aren't prepared for and desensitized to the rigors of retail campaigning have an early vote. We can't just give the roles of first and second state to states that aren't primed for that kind of intensity. They'd get pissed off at the campaigns' persistence whereas we know it's all in the game. If any states are going to go first and second, they have to be Iowa and New Hampshire. But if they keep their first in the nation status, things like Michigan will keep happening. Things like Florida will keep happening. The DNC will have to decide how to punish states like that, and if they do so when the popular vote's close, the same chaos we saw this year will repeat itself. In sum, we can't have staggered primaries without massive problems of some sort or another. There needs to be a national primary. This works well with preference voting; with staggered primaries with preference voting, you could conceivably calculate the result after each group of states votes, but it'd be hard to know how to interpret that. But with a national primary with a single deadline, there'd be no mindless speculation and punditry about these counts.
5. Postal voting:
It increases voter turnout, prevents voter suppression, and limits the importance of local machine in GOTV operations. What's more, it would allow the party to run elections without any involvement of the part of local governments. The DNC could conceivably mail every registered Democrat, and every Independent and Republican who requests one, a ballot, have them sent to headquarters in DC, and do a national tally without regard to state or territorial boundaries.
So that's my proposal. A DNC-run, open, national postal primary, with the result determined by Schulze ranked voting. Will it happen? Of course not. Would it be far, far preferable to the current system? Definitely. And, most importantly, would all the myriad catastrophes of this primary season been avoided under my plan? Without a doubt.