Bear in mind that users may not reach your document through your homepage, but directly using a search engine or link at another site, so the title should ideally be self-sufficient. The description is presented to the user along with the document's title as the result of a search. Many robots use the first few lines of text as a description if the Description tag is not present. For documents using frames, it is possible that there is no such text present. For an academic text, this should probably be the abstract.
Some robots look at keywords in context, so it is best to preserve word order and case.
Separate keywords by a comma with a space around the commas. Include 2-3 word phrases as well. The organisation hosting the Web page, perhaps. The geographic coverage of the resource. Click here for more information.