The idea for this post came from the awesome Ferrett Steinmetz, who told me he thought choosing stories for an anthology was like making a mix tape. So here's what I think of that.
There are different kinds of anthologies. Reprint anthologies are made up of stories that have been published before in other places. The editor picks a theme and chooses stories to fit that theme. Making a reprint anthology is very much like making a mix tape. When I make a mix tape, I'm usually making it for someone else, to combine songs I like in a way that I hope they'll enjoy, that might create a different effect from listening to the songs as part of their albums of origin. I might include more obscure songs so that I can be a showoff about the range of my musical interests, while bringing some more popular songs to keep the mix accessible. Likewise, with a reprint anthology you look at stories that have already been chosen for publication in various places, and evaluate how well they would fit into the effect you're trying to achieve. You can select from a huge range of stories, published over a long period of time, and this gives you the opportunity to use stories written by Big Names with Big Followings, although many people will have already read at least some of those.
Then you have original anthologies, for which writers are asked to submit previously-unpublished stories to fit a theme, and that means they may be writing new stories specifically in the hope of having work published in that anthology. This process is a little bit like making a mix tape, but it's a lot more like commissioning musicians to write songs for a new album. It's about bringing something new into the world. There's collaboration involved. The editor needs to be able to write effective guidelines that will get writers to understand what kind of stories she wants, and for that to happen, she needs to have a clear idea of what she wants in the first place.
Deciding who to ask to submit a story is complicated. Do you ask everybody, making it an open call for submissions and posting about it all over the place, to bring in lots of potential material and maybe some surprising gems in the form of a huge slush pile to read through? Or do you think about which writers are already doing the kind of work you like, and invite a select list? Because that way you minimize the work and maximize the likelihood of getting the kind of stories you want, but you don't give anyone new any opportunities and you don't get major surprises. It's in your best interest to ask some well-known authors to submit stories, but they're the ones most likely to be busy or to not need to be in your little anthology because their collection of every story they ever wrote is coming out next month. But if you're paying attention, maybe you can interest some emerging writers who have been steadily writing new, awesome work and getting new, awesome fans eager to see what they'll write next.
Once the submissions come in, the editor needs to be able to evaluate them on an individual basis for: 1) how well they suit the anthology's theme, 2) how well they work as stories, and 3) if they're not quite right in either of the above areas, whether or not they can be edited into becoming right, and whether or not the amount of editing necessary will be worth the effort. It's possible that a story that doesn't work for this anthology might be perfect for another one, or might sell somewhere else without much editing.
There are decisions to be made about how well the stories will work together. Maybe some of them are too similar to each other. Maybe one is great, but so different from the others that it wouldn't make sense to keep it. Then there's the order of the stories to decide. Given the way they all go together, which one is the strongest candidate to go first? Which one will be best to finish off the book and leave the final impression? (These are considerations in a reprint anthology, too).
Another way is to combine both types and create a book with some original stories and some reprints. This may be the strongest option if you prefer the original type, combining the unknowns of novelty with the flexibility to fill gaps with known authors' work. If you don't receive enough of the kind of stories you were hoping for, you can go shopping in the store of magazines, collections, and other anthologies to find already-polished stories that have been tested and reviewed. Or if you're starting from the reprint plan, you might want to tempt readers with a few stories that have never appeared anywhere else.
In conclusion, what I'm doing with What Fates Impose--an original anthology of fantasy stories about divination, which may include a few reprints--is bigger and messier than making a mix tape, but it gives me the chance to contribute more and make more decisions than a reprint anthology would, and I love it.