This is a rough outline of the process for Working Group 1, leading up to the first public draft milestone:
For voting we will use a preferential voting mechanism, so that any number of proposals can be made without detracting from each other or forcing an all-or-nothing situation. The exact method remains to be decided, but will likely be either ranked pairs or Schultz. In addition to winning the vote, any deviation from R5RS must beat the R5RS option by a minimum percentage, yet to be decided but likely in the 75-90% range.
A detailed example of the voting process can be found in the Yak Handler proposal.
The hope is that with this system and a more or less balanced representation of Scheme implementations and ideals among the members, we can ensure that while nothing crazy gets added, any feature that is almost universally desired _will_ get accepted, even if we can't agree on all the details.
Overall it's important that Working Group 1 err on the side of conservatism, to ensure a wider acceptance among implementations than R6RS received. It's harder to remove features than to add them, and we have Working Group 2 to add any extra features necessary.