Conventions for the PATH variable's value

I am looking for best practices, or at least conventions, for the PATH variable's value. In particular, I would like to know 1. is there any preferred/recommended ordering for the /bin, /usr/bin, and /usr/local/bin directories in the value of PATH? 2. are there any downsides to including /sbin, /usr/sbin, and/or /usr/local/sbin in a non-root user's PATH variable? Regarding (1), my uninformed opinion is that these paths should appear in the order ..:/usr/local/bin:...:/usr/bin:...:/bin:... ...in the PATH variable. The thinking here (to the extent there is any) is that /usr/local/bin may be where a local installation would put a "local" override of a command that may also exist under /usr/bin. By the same token (and now really stretching it!), /usr/bin may contain distro-/vendor-level overrides to commands that traditionally live under /bin. I realize that the above is 99% fantasy. That's why I am asking this question. In a similarly hallucinatory vein, I seem to recall the notion that the commands in */sbin directories are meant for folks with superuser privileges, and it would confuse the regular users' little brains to make these commands available to them. In other words, the PATH variable for regular users should not include any */sbin paths. Be that as it may, I don't recall ever coming across a system that included */sbin paths in the initial setting of the PATH variable (by this I mean the setting of PATH that each user gets before his/her shell initialization scripts are run), and I wonder why this is so.