Just seconding what joong said.. this already covers our original, simple and inadequate guideline "do not vote unless there is at least one comment"..
PS: We have lost 2 12hour games already on timeouts, so I think it makes sense to create future games as 24hours or more..
The most important factor in winning vote chess games (besides not timing out) is to avoid voting for a blunder before the whole group has the chance to discuss the move. To that end, i'd suggest we reserve the first half of our voting window for discussion only.
That means we should each wait till the second half before casting our vote. Please discuss your move before casting your vote if no one has suggested it yet. It's good to start the discussion as early as possible to give others more time to consider your move. Of course there are always exceptions, so if you feel that a move is forced or the choices don't matter too much as in the beginning of the game AND you might not be online to vote in the second half of the voting window, then please go ahead and vote right away.
Because making everyone wait for the second half to vote increases the chances of timing out, we should designate 1 or 2 admins to make sure we always submit at least one vote so we don't time out. They would be allowed to vote early if necessary.