So once again I had a file that I nee­ded to save in UTF8, because the ori­gi­nal for­mat it came in was dif­fe­rent. And time and again, I had to chase down the appro­priate thing in the Emacs docu­men­ta­tion. So here is how to do it:
C-x [RET] f CODING [RET]
CODING is the coding for­mat; com­ple­tion is avail­able.
And you find the docu­men­ta­tion in the Text Coding Node of the Emacs documentation.