This summer, you’ll quickly discover that writing well is a critical skill for every lawyer—and anyone who wants to be a lawyer. Legal dramas often give the impression that oral and theatrical skills are paramount. But make no mistake: writing is the main way lawyers communicate with each other, with judges and other decision-makers, and with their clients. 

Now, you may think that because you can already write well, and because you’ve already done so much writing in law school, writing...