I don't believe I've mentioned this website before (and if I have, it's worth repeating), but for writers aspiring to publish, Duotrope's Digest should be one of your top bookmarks. It's a virtual clearinghouse of information on journals and lit mags. You can search by genres and subgenres (mystery, sci-fi, literary, etc.), styles (realist, experimental, humorous, etc.), payscale, medium (print, online, audio broadcast), submission type (print and/or email submissions accepted), and more.
So before submitting to the Missouri Review, you can learn that they accept less than .25% (and yes I mean that period there) of submissions (and also yes, I know this is a percentage of people who report it on Duotrope's Digest--it's possible that the percentage is much lower--think of all the people who submit and don't even know they can report it on the Digest). So newbie writers might stop and think--hmmm, less than 1 in 400 submissions is accepted. Maybe this isn't the place to send that story you just wrote for your first creative writing class.
Information such as how soon you can expect to hear from a journal (average 2.6 days for Bananafish, average 309 days for McSweeney's Quarterly) and the aforementioned rate of acceptance (.23% for Missouri Review, 91.43% for Daily Bites of Flesh 2011) goes a long way to helping a writer get some publication credits (I know where I'm sending my next horror microfiction "bite of flesh").
Another useful feature is a list of upcoming theme deadlines. This can also be a great place for new writers looking to break in. My guess is that not so many people are writing stories about Australian Vampires, Adopted Chinese girls or What a Woman of 45 Ought to Know (all theme issues currently looking for content). I like to peruse the list and see if there's anything I've written that fits themes. If you're written about aliens, the aftermath of 2012, or the American dream; science, slumber, or secrets; creation, the courtroom, or yes, even cat crimes, there is presently a journal or anthology looking for your work.
There's a lot more worth describing, but it's a fun site to explore, so go take a peek.