shared folder

When two users on Linux need to share files, accession rights can be quite a problem. By default only the one who creates the file can read and modify it, even if it is saved in a directory that is accessible by the other. It appears to me still impossible to solve this problem completely as Linux cannot "inherit" privileges to newly creates/saved files based on their parent directories privileges (BTW: how has Mac OS X solved this problem?)

The following instructions create a shared directory, but require additional tweaks.
As root