Tip: Unless an editor specifically asks for a list of credits, provide a two to three sentence bio. Period.
Why is this important? Simple: When I have to scroll through a list of credentials to get to an actual submission, you've already stolen some thunder from your work. I frequently get bios of three or more dense paragraphs before a submitted work. By the time I get to the story or poem, I'm a little less curious than I was when I opened the email.
Also, while some writers write blissfully brief bios (which should be in the third person), they then give me a lengthy list of credentials, again, before the submitted work. If you really feel the need to let me know what you've accomplished, do it after the submission. That way the story or poem shines right away.
When you write for any project I am affiliated with, you need to remember that it's the work you submit that counts. And, in any case, I often publish first-time authors.
I don't give personal feedback, but I'm going to start writing tips here at EC. I hope you'll take it off in the spirit of help, which really is why I am doing it.
Eye candy by Virginia Frances Sterrett.