Part of the conversation is about whether or not it's worth it for a writer to submit to markets that pay less than SFWA pro rates--that would be five cents a word.
Now, if you want my personal advice, you want to consider two--maybe three--things when deciding whether to submit somewhere. You, as a writer, want money, yes, of course, and you also want eyeballs. You want people to read your work. Usually--not always, but usually--the money is a good indicator of the actual number of readers a particular venue has. There are a few zines where this doesn't match up, where token payments go along with "lots of people read this" and/or the "maybe" third--"this zine has a good critical reputation." Token payment doesn't necessarily mean nobody reads it or it's not worth being published there. Knowing which places those are--well, that requires paying attention to the field, doesn't it? Gotta do your homework.
Which leads me to the thing I actually want to talk about today. Everytime this sort of conversation comes up, someone--often several someones!--argue that newbie writers have to sub to low-paying, tiny markets because that's how you get credits to put in your cover letter, and that's what makes an editor actually pay attention to your story.
No. NO! This is wrong. This is so wrong, I'm not sure the English language is able to express just how wrong it is.
Look, I read slush. Here's the bottom line: The thing that makes an editor pay attention to your story is a kick-ass story. Period. The End. It doesn't matter if you have good credits, or any credits at all.
Now, it's true if you have good credits you can sometimes jump the slushreader. It's true that if you have good credits, an editor will start reading with the expectation that what she's about to read is not, in fact, going to be the sort of headdesky slush that gives the slushpile its name and reputation--a reputation, I might add, that is thoroughly deserved.
But its also true--I am telling you this on my honor, I swear this is absolute truth--that if the slush reader rejected you, jumping the slush reader would not have helped you. I swear it. If JJA rejects you, over at F&SF, I swear to you on my sainted grandmother's grave, Gordon would have done the same if he'd seen your story.
And it is absolutely true that if your story totally rocks, if it's compelling, the editor will sit up and take notice. She will pay attention. Whether you have credits or not. No, really. The editor does not actually care about your credits. She cares about the story.
Now, as I said, "good" credits will lead an editor to expect, before she ever starts reading, that your story is at least going to be readable. This will give you a little leeway--maybe a bit more patience with a slow or otherwise dubious start.
But just any old random credits? Will not help you. In fact--and I hesitate to say this, but I'm going to be very honest here--there are credits that can have the opposite effect.
No, I'm not going to tell you what they are. Some of them are just personal to me, zines that might pay decently or have a good reputation, but I have rarely been bowled over by what I've read there. Others...well. When I read a cover letter that tells me the author was published in "Fairly Reputable Journal of Stories Ann Doesn't Like" and/or "Tiny Zine That Pays Nothing and Ann Doesn't Really Like Anything They've Published" I find myself not quite so enthusiastic about reading the sub. And when a cover letter claims credits from ten to twenty small zines and maybe I've heard of one of them*...I am not particularly impressed.
Those credits will not get you a better shot with the editor. They just won't.
Now, I read every story anyway. Because that's what the job is all about. And I pass up the stuff that needs to be passed up, no matter what. Credits are irrelevant.
There is no point in submitting to a tiny market for no pay just to get a credit you can put in a cover letter. That credit is useless to you. If you are being relentlessly rejected by well-regarded publications, it's not because you have "no credits," it's because you need to step up your game. Seriously.
There's a slim chance that you're consistently being bounced by the slushreader because you are a genius who is ahead of your time, or because the sort of thing you do just isn't in style even though your work is utterly brilliant.
There's also a slim chance that you could jump out of an airplane with no parachute and survive.
Where's the smart money?
Aim high. Those 4-the-luv markets aren't your first stepping stone on the way to the pros. If the pros are what you're aiming for then for pete's sake, aim for the pros.
That said. When you run out of high-pay, high-reputation places to send your story, by all means, move down the line. Myself, I'd rather get ten dollars for a story than nothing at all. Though of course I'd rather get ten dollars from somewhere that I know people read, and I personally don't submit to places that as far as I can tell don't have readers to speak of. Your personal cutoff may be different, and that's fine. I'm not here to tell you who to submit to, and who not to submit to.
I'm just telling you, if you're submitting somewhere only because you think it's necessary to have some credit, any credit! on a cover letter, that any credit at all that you can scrape up will make an editor pay more attention to your story, you're absolutely dead wrong. The credits that will give you a (slight) edge are precisely those professional markets you're trying (and failing) to impress. And no credit in the world will make up for writing that isn't up to standard.
Don't worry about credits. Just write better.
*I troll ralan and duotrope just like every other writer. I pay attention to the conversations going on in the community. I know what stories, and what publications, people are talking about, and hence reading. If I haven't heard of it, chances are not many people are reading it. This is not an infallible rule--but it's held up well over time.