At thoughtbot we've recently started to redo our outdated coding standards. We've taken a consider everything approach. Making the easy decisions by fiat and then opening up some of the decisions to the discussion of the entire group (with one person given ultimate responsibility for making the decision).
Its going well, but slowly, so far. When we did our original coding guidelines a few years ago, it was decided that we would use a different curly brace style than I was used to at the time. It took about two days to get used to the new format, but then after that, I couldn't see them any other way.
My main point is that when it comes to guidelines, its important to be flexible. What may seem the wrong way to do something one day, can easily be the right way the next, if you commit to the change. And as programmers, what we may think are permanently ingrained ways of doing things, can almost certainly be changed.
Our new coding guidelines are pretty much entirely Ruby and Ruby on Rails focused. Anyone out there have any helpful hints or interesting stories about your Ruby and Rails coding guidelines?