Two years ago, at the Dagstuhl seminar 08431: Moderately Exponential Time Algorithms I was asked to join Dieter Kratsch, Gregory Sorkin, and Ramamohan Paturi to propose a new seminar for 2010.
Here’s how that works.
Dagstuhl expects a written proposal for the proposed seminar, see Dagstuhl’s submission guidelines.
By February 2009, we had an early draft of the proposal ready, and polished it in the following weeks. The most rewarding part was writing the scientific motivation, which turned out as a really good overview of the field of exponential time computation as of Winter 2008. I made a separate blog post of it:

Total number of emails in my inbox in 2009 and 2010 in connection with organising Dagstuhl Seminar 10441, November 2010
The other big task is the list of people to invite. Dagstuhl seminars are by invitation, and a preliminary guest list is submitted by the organisers together with the proposal. Dagstuhl has room for 50 people or so, and we were asked to concoct a non-binding list of 80 potential invitees.
We submitted our proposal time, in early April. I can count some 90 emails between the organisers in my inbox for that part of the process. After the Summer 2009, we got a positive reply from Dagstuhl, together with dates (November 2010).
Next task: assemble the true list of 80 invitees, so that the Dagstuhl office could send out the invitations roughly one year in advance. Also, this list should be partitioned into two rounds of 60 and 20 people, respectively. Dagstuhl then sent out the first 60, using the others when they got refusals back peu à peu. All communication was handled conveniently by the very professional Dagstuhl officers, who regularly kept us up-to-date about the invitation status.
Our hope was that everybody on our 80 people list would be invited, but this turned out to be far from the case. Apparently, acceptance was very high, leaving many very good people uninvited.
Dagstuhl-related emails in late 2009: Maybe 20. Letters of invitation arrived in people’s inboxes January 2010. Yes, that’s physical mail. It’s like the Internet, but made out of trees.
In the first half of 2010, I count 52 emails between the organisers, mainly about individual guests, such as people who hadn’t replied, though they told somebody over coffee they’d surely come, etc. By July, we seemed to have 49 acceptances, at which point Dagstuhl would not invite more people.
Most of the remaining organisation tasks, again, were handled by Dagstuhl: Setting up a web page for Dagstuhl Seminar 10441, sending out travel information, etc.
Among the organisers, we started to talk about the seminar format: how many talks, how to select and schedule, etc., leading to a respectable number of 68 more emails. Most notably, the very last days before the meeting became hectic because of a number of last-minute cancellations.
The seminar itself was stress-free, and I really enjoyed myself. There was some extra organising work with respect to scheduling, arranging an excursion, etc., but for almost everything one can rely fully on the very experienced Dagstuhl environment. It feels extremely reassuring that every little situation that comes up has been handled countless times before, be it by the Dagstuhl staff, the local taxi company, or the restaurant owner arranging the wine tasting.
After the meeting, we wrote a brief thank-you note to the attendees. What remains now is some wrap-up work: a final report, list of open problems, etc.
Oh, and think about the next proposal.