Footnotes and Superscript.

I've always been curious when and where one should use Footnotes and Superscript. When does it become necessary to footnote, and what justifies the use of superscript? I've often read books or essays that contain superscript and I always enjoy how neat and tidy it can make a specific text look.

I've learned (the hard way) that superscript should not be substituted for citation. I'm hoping to learn a little more on this subject since we, as editors, need to know when to make such corrections or suggestions to an author.

-Davis Hoffman