On Tabs and Spaces

What are the rules about tabs and spaces in source code?

I'm having a terrible time with formatting,
especially in the perl scripts; there is a
mix of spaces and tabs.

from what I can deduce, single tabs are used
to introduce the equivalent of 8 spaces while
4 explicit spaces are used for half a tab.

I would recommend using all spaces, but the C
code seems to prefer all tabs.

In any case, some kind of standards need to be
set, because no one is following anything curr-
ently.

Sincerely,
Michael Witten