The Occupation Thesaurus: A Writer's Guide to Jobs, Vocations, and Careers by Angela Ackerman & Becca Puglisi is another book in the Thesaurus series of writing support books that gives you details on various occupations. Common traits, common skills, common conflicts they are involved in.  A great resource for making a more well-rounded, less cliche characters.

Definitely another one a writer should be keeping in their library.