Today agents Janet Reid and Colleen Lindsay have both blogged complaints about writers including extraneous publishing credits in their queries, so here are some guidelines:
Contests: Ms. Reid says agents do NOT want to hear about your 3rd place or hon. mention “wins”. It’s first place or nothing. She says if you didn’t win, you LOST, and it isn’t something to brag about.
I guess that makes sense, although I’d use discretion here. If it’s a prestigious contest and you won something that’s an equivalent of an Olympic “Bronze,” I’d say go ahead and put it in. If it’s more like you got on the team but spent the entire game on the bench, leave it out. The complete post is at http://jetreidliterary.blogspot.com/2010/01/contests-in-your-query.html.
Short Fiction and other Journal Publications: Ms. Lindsay has a wonderfully detailed post telling exactly what she wants to hear and what she considers a waste of her reading time at http://theswivet.blogspot.com/2008/11/reader-question-when-should-you.html.
With short fiction, if you’ve got a credit in a publication that’s available nationally and/or she’s likely to have heard of it, she’s eager to know. If it’s your brother-in-law’s advertising circular, not so much.
With non-fiction articles, she's only interested if they’re relevant. That means that even if your work on urinary incontinence appeared in the Journal of the American Medical Association, or you’ve placed twenty op ed pieces in the Times on the subject of global warming, agents don’t want to hear about it. Agents don’t consider them good indications of whether you can keep the sexual tension going in a werewolf romance.
Ditto Non-fic Book Credits. Even if you’ve written Sunset’s most popular book on building doghouses, if you’re pitching an apocalyptic thriller—keep the Fido condos to yourself.
As far as Published Novels, Nathan Bransford has a great post on the subject at http://blog.nathanbransford.com/2008/03/how-and-whether-to-list-your-publishing.html .
He's OK hearing about any novels you’ve published, as long as you provide the publisher’s name and year of publication. He says it’s OK to mention if you self-published—AS LONG AS YOU DON’T CALL YOURSELF A “PUBLISHED AUTHOR.” “Published” to professionals means you’ve been vetted by a number of editors and marketers—and publishing businessfolk have been willing to put up hard cash because they believed in your work.
In other words, when in doubt, DON’T list list a credit. As Nathan says:
“The ranks of people who have been published without a single credit to their name are legion. Just say "This is my first novel" and say it proud.”