I worked at the Laurel Review/Greentower Press, which is a literary magazine and a small press at NWMSU, ages ago, for a summer semester. I guess I was an editorial assistant, because I read slush and helped them get stuff mailed out, but mostly I was helping them adjust after their move to a different building (Colden Hall was being remodeled). So I was doing a lot of book-stacking and room organizing, too. But as a wide-eyed young writer I was fascinated.
This is how things worked at a literary magazine. The editors and the readers would read the MSS and, if a MS struck them as possibly being worthy, they'd scribble a comment on the envelopes the MS came in. "Take a look at this," or, "Not sure but maybe take a look," or, "What's with the screaming guy?"
The noteworthy submissions were set aside and given a second look. If the material was good but didn't fit in with the magazine's style, or if the ending didn't work, but they still liked the writing, they'd give it a "kiss," aka a form letter that said "try us again." All the rest of the MSS got form rejections.
Manuscripts that were accepted became proofs. On the original MSS, in red ink, one of the editors would specify margin width, page setup, font style and font size. Of course the MSS were proofread and made to conform to house style. Then a big sheaf of MSS would zip off to the printers.
After the magazine had been published these marked-up proofs would end up in the recycle bins. After asking Dr. Slater, I pounced on them and took 'em home. Among them was a couple of poems by Galway Kinsey, I believe. I kept those!
The last time I stopped by the LR offices, there were two recycle bins overflowing with rejected submissions, and a big pile of new submissions that needed to be read. Just so you know.
Most literary magazines have professors as their editors, and if they're good professors (and the guys I worked with were quite good), they're running all over the place taking care of their students, and in their spare time they run the magazine. This is why it takes a while for them to get back with you. Finals week is really bad. And don't send stuff in summer because often there's only a wide-eyed young writer running things.
Small literary magazines often send out requests for subscriptions with their rejection letters because they really could use the subscriptions! A lot of magazines survive on grants and magazine sales, not on advertising. Advertising is traded between magazines -- "I'll show an ad for your magazine if you show an ad for mine." Kind of interesting.
I think nearly all of the LR editors have retired -- I know Trowbridge and Slater have, though I'm not sure about Dr. Richards -- and there's a new generation in place. But I'm pretty sure things are still run the same way. And as far as I can tell, the new editors are pretty sharp, too, though I don't see them as much as the old-school guys.
If you live near a university, you might volunteer at a local lit magazine. It is a real eye-opener (and also you get to read real slush!). And any time an author can spend behind an editor's desk is time that pays back in understanding and patience, as well as a better sense of what a writer can get away with ... or can't.