The instruction page for PBP pre-registration includes the pre-registration schedule.
The instructions indicate that riders will need rider affiliation, rider license number and homologation number of longest 2010 brevet, but I'm fairly certain that for riders' whose affiliation is "Foreign" (i.e., non-France), the rider license number is inapplicable.
RUSA members can find the homologation numbers of any 2010 US ACP (200, 300, 400, 600, 1000) or RM (1200 or longer) events by results search on RUSA website. Homologation numbers for non-US RM events can be found at http://www.lesrandonneursmondiaux.org/homologations2011.html. For non-US ACP events, riders will probably need to consult the event organizers.
For clarity - note that the ACP uses the term "homologation number" and the RUSA results search function will give you a "Cert. No." for your brevet result. These are the same thing.
For a 2010 1000km brevet, it's probably a number in the 6000s. For a 2010 RM 1200km+ brevet, its a number in the 4000s. In the case of an RM brevet, please just use the numeric part (ignore the leading "US-") when pre-registering.
Bengt from Sweden posted today that you will indicate your choice of start time at pre-registration but that it can be changed with the final registration in June.
You'll need a credit card for the pre-registration deposit and your certificate number. I think that the registration is supposed to open on 4/3 at midnight, which would be the previous afternoon here. No need to rush, however, because it's not possible for the US quota to fill up this weekend. We just didn't have that many 1000/1200 riders.