Mary Beard has a good discussion of footnotes in her TLS column. Here’s the beginning:

I know what I like, and don’t like, in a footnote: an accurate and precise reference to what ever is being discussed (I mean not a reference to Smith (2008), when Smith (2008) is a book of 1000 pages — but Smith (2008) 245-47); a certain modesty (not a vast multi-lingual bibliography of modern theoretical works, semi-relevant to the topic, designed only to display the learning of the author… you know ‘the seminal work in Slovenian remains..’); and value-added wit (I like a footnote to reward those who bother to consult it with an extra bit of thought-provocation and humour).

But it is one thing knowing what one likes, quite another actually managing to do it oneself.

I have spent the last week or so trying to complete and check the footnotes from my book of the Sather lectures (on Roman Laughter), now long overdue. And a rather gloomy experience it has been…