A good book just got better:
Thomas R. Schreiner. Interpreting the Pauline Epistles. 2nd ed. Grand Rapids: Baker, 2011. 
From the preface to the 2nd edition (p. ix, line breaks added):
It is tempting to enlarge the book significantly, but I believe the book has continued to be read because of its brevity. Hence, the purpose of the revision is to update the book where necessary, especially in terms of bibliography.
The book has not changed dramatically, for I am still convinced that the substance of what I wrote some twenty years ago is correct. Nevertheless, the entire book has been revised, and there are some significant additions.
The original edition presented the diagrams in Greek but not in English, and thus English has been added to enable readers to understand diagramming conventions.
The most valuable chapter in this book—or at least the one that most strongly influenced me—is “Tracing the Argument” (pp. 97–124). It revolutionized how I read Paul.
Update: That chapter is available as a PDF (though it’s from the first edition, not the second).
Update on 3/31/2017: In my latest attempt to explain how to interpret and apply the Bible, I include a chapter on argument diagrams with a focus on phrasing (pp. 121–61).
This is indeed a very good book, but those particularly interested in the method of interpretation described in the chapter “Tracing the Argument” can also consult http://www.biblearc.com
The method Schreiner calls “tracing” is alternatively known as “arcing,” and the website mentioned above contains a free video tutorial explaining the method. Additionally, you can practice tracing/arcing on the site for free, and for a $10 per year fee, you can store your own traces/arcs on the website and compare with others who have done work on the same passages. The website is owned by the Bethlehem College and Seminary.
(Although this sounds like a paid advertisement, I do not work for http://www.biblearc.com or Bethlehem College and Seminary; I am simply an enthusiastic advocate of the method Schreiner discusses that Andy too found helpful. I find it really helpful, and I would love for more people to employ this useful tool.)