Google unusual titles, sentence fragments or theses to ascertain if they have been used before and in what way. Compare the overall writing style and ability of the paper with the student's known and previous work. An entire industry has developed to conduct an in-depth form of this type of research for professors, publishers and employers. Turnitin.com is one example.
Compare the paper's published book bibliography against your university's library catalog or your local public library. Ask the student to clarify cited sources that are not physically available through these channels.
Keep a file of paper titles and bibliographies. Compare current papers against those students have submitted in the past. If is helpful if you and your departmental colleagues collaborate for a shared file and larger database.