If you find a seed article, or any other really good article, we have a magic database, called the ISI Citation Database, which can find all the other articles which have cited that article, either because they support it or because they disagree with it.
The ISI Citation Database is on our database list under ISI Web of Science.
Go to “Cited Reference Search” and type in the author’s last name, the journal in which his article appeared and the year it appeared in the appropriate boxes. This will bring up the authors and articles that have followed or disagreed with that author.
Unfortunately this database is not full text, but you can often get the full text of the articles off one or other of our alternative databases.
Google Scholar does something similar. Find your article of interest, and click on the "Cited by" link.
Next topic: Step 6: Find agreement & disageement