Every Friday, Chicago-based writer and editor Evan Peterson offers five stories that scribes of all stripes should check out. It’s the Week in Writing:

Also, some writing advice from Colson Whitehead, Susan Sontag, and The New Yorker's editor-in-chief.

A Writer's Credentials. What does it take to be a professional critic for a newspaper? Does the person need to have studied the topic he or she is critiquing, or done it in a professional manner? Should a film critic have a background in film—academic or professional—to write movie reviews. Not necessarily, according to Jonathan Landman, The New York Times' culture editor. “The credential that marks a great critic is great criticism,” he wrote this week in response to a reader, who asked that the paper cite the credentials of its critics.

As bloggers, copywriters, and ghostwriters, we're rarely writing criticism. But in his response, Landman made a point that is bulletin-board worthy for the corporate communications profession.

“Among famous movie critics, Andrew Sarris and Vincent Canby had nothing fancier than bachelor’s degrees and Pauline Kael dropped out of college, yet millions devoured their work with pleasure and respect. There are also journals full of articles by credentialed film scholars. Whose stuff would you rather read?”

Basically, there will always be people who know our subject matter than we do. But we get paid to write about it because we explain the material in a more interesting and palatable way. Read Landman's full response here.

The Art of the Profile. Longform journalism is experiencing a resurgence, and one of its cornerstones is the celebrity profile. The New Yorker's editor-in-chief David Remnick talks in this piece about what makes a quality profile, and how he went about constructing a recent piece on Bruce Springsteen. Among other things, he notes the exaggerated value of access, and how some of the best pieces—most notably Gay Talese's profile of Frank Sinatra—succeed without it. Read the story here.

Double Commas. Comma philosophies are as disparate as political philosophies, and often more strongly held. But hear this one out. Some editors, including the author of this piece from The Christian Science Monitor, hold that commas can, and perhaps should, be used as much for "stage direction" as for anything else. That is, to give the reader a breath, placing the commas where a natural pause might go, or to emphasize a point. One extension of this is that commas always come in pairs, like parentheses or quotation marks. Read the full story here.

Colson Whitehead's Writing Rules. The author of several novels goes through 11 rules on how to write, one of which is secret and another which lets us know there are no rules. The other nine are helpful, and include new iterations of rules you've probably heard in the past. Check them all out here.

Susan Sontag on Writing. BrainPickings.com pages through newly published diaries from Susan Sontag to find some of her best quotes about the writing craft. BrainPickings’ editor and curator Maria Popova writes that—unlike advice from other famous writers—Sontag's lessons are more introspective than prescriptive. They include: "A writer, like an athlete, must ‘train’ every day. What did I do today to keep in ‘form’?" Read the post here.

Evan Peterson is a writer based in Chicago, and the editor of OpenMarkets magazine at CME Group. He's on Twitter at @evanmpeterson.