Ask HN: Simple company policies or guidelines that work well?

The other day there was a great side-discussion on a company's book buying policy (http://news.ycombinator.com/item?id=1639193) which seemed so refreshing compared to the ones I have seen. One point that I liked was that it could have been made into a one liner, but in practice a more detailed (but still simple to follow) guide worked well since it made employee's more comfortable on how to use it. Anyone else have some simple (and real life) examples of policies, guidelines, or procedures that have worked well?