which character set am I using?

Hi,

How do I work out what character set my editor is using, if it doesn't
tell me, and I need to declare the correct one in my HTML headers?

* Hex-read the document, and find the codes for a few specific characters?

* Assume all documents written on this computer use the same character set?

* Hope that I can declare a basic ASCII one, if I don't type anything
  other than standard typewriter symbols?

* Is there some easier or better way?

I notice that even the page listing the threads in this discussion didn't
validate, because it didn't mention a character set.

-- 
Tim