When I was a teenager I discovered at my local library a fascinating book called Writer's Market. This book was a monster, a 1008-page leviathon that would put most college textbooks to shame, and it was filled cover-to-cover with small-print listings of newspapers, magazines and anthologies where I could submit my writing.
Writer's Market was a revelation for me. As a novice author, I'd assumed that the two or three science fiction magazines I knew of were the only ones there were. It had never occurred to me that there might be so many different places where I could submit my fiction.
Today, thanks to the internet age, it is no longer necessary to pore over pages of microscopic script in order to submit your fiction. There are a number of online venues that specialize in providing just such information. Allow me to share some of my favorites.
Duotrope is a free, internet-based listing of over 2000 markets for fiction and poetry. Market entries are searchable by genre, pay rate, manuscript length, and a number of other factors, and they include statistics about how long on average the editor tends to take to respond.
Ralan's market listings focus exclusively on speculative fiction; that is, science fiction, fantasy, horror and related genres. He has them handily separated into professional, semi-pro and 4-the-luv (non-paying) markets, with a special category for contests. Ralan keeps his market listings exceptionally up-to-date and also provides a warning if a small-press magazine has gone out of business or stopped responding to submissions.
The Black Hole
This is more of a response-time-tracker than a market listing, but for new writers biting their nails and wondering whether their manuscript has been lost in the mail, it can be a godsend. The basic principle is one of communication: authors report how long it took them to get an acceptance or rejection letter from a given market, and those reports are used to provide statistical information.
With such a flood of potential markets to send their stories -- and with new markets opening up all the time -- it's sometimes hard to know where to send your story first. Everyone finds their own strategy over time, but here are some factors most authors look at:
Does My Story Match the Market?
All magazines are not created equal, and submitting your story to a magazine it's not well-suited for is a waste of time for you and the editor both.
Do not assume that just because your story is science fiction (or fantasy, or horror) and the market is listed as accepting that genre, that your story is necessarily a good match. Some editors prefer adventurous, upbeat fiction. Others prefer realism. Some place a high priority on wordcraft and characterization. Others pay more attention to plot and pacing.
Take time to get a feel for what kinds of stories the different magazines publish. This is not as expensive as it might sound. Many magazines make their Hugo- and Nebula-nominated stories available online at Awards time, and a number of online magazines have content that's freely availalbe year-round.
What's the Pay Rate?
For speculative fiction, markets that pay five cents per word or higher are generally considered professional markets. Markets that pay between three and five cents per word are called semi-pro or semi-professional. There are also markets that pay fixed rates, pay in copies, or don't pay anything at all.
Among authors of my acquaintance, the generally accepted rule is: Always submit to the highest paying markets first.
Many authors are tempted to spare themselves the pain (and postage costs) of receiving five, ten or even a dozen rejections before selling the story, but I would advise against this. Give your work a shot at the best market in the field. It may fail, but then at least you'll know that. If you sell it to a low-paying market on its first trip out, you'll alway wonder whether it could have done better.
What's the Response Time?
The time it takes from submitting your manuscript to receiving a rejection (or acceptance!) letter varies dramatically. Some online magazines respond in days or even hours. Other markets require over a year to respond. Many authors are unwilling to wait that long for feedback no matter how high the pay is, and so skip over the markets with unusually long response times.
How Reliable is the Market?
Fiction markets are not static. New magazines spring up and others go out of business with occassionally distressing regularity. Many authors are cautious when submitting to markets less than one or two years old, as experience has shown that they sometimes fold after a story is purchased but before it has ever seen print.
These aren't the only factors you'll want to take into account when submitting stories, of course, but they're a good set to start with. Over time, you'll get a feel for what's important to you and what isn't.
Keep at it, good luck, and don't forget Heinlein's Rules.
Go get 'em!