What's also good is to establish a procedure to change the guidelines. It can be a source of frustration to have some funky guideline that most of the team doesn't like.
that's what the wednesday afternoon is for, changing our way of working. But we sometimes do it before.
We've a problem with our python formatting guidelines, and I'll bring the issue tomorrow I think (we've to decide for spaces or tabs and camelcase or underscore, since it's not our only language, we've to arbitrage between a common rule for all our languages, or the usual rule of each language).