Let's say you have a short story in an anthology. What do you do next? Terri DelCampo has some in a couple of anthologies published by Lycan Valley Press. I have quite a few with a number of different publishers. Do we just sit on our laurels and figure we did our share? The answer is a resounding no!
For however long the anthology is published, an author should help to promote it. There are a number of reasons for this. The publisher invested money in each author and it's a big help when authors help with the promotion. Then too, the more you promote the book, the higher your rankings will go when books are sold, whether it be via Amazon or any of the other outlets. When your rankings go up, people will see what kind of books you have and check out not only your latest anthology, but your other books as well.
Does this matter if you received payment for your story? Even more so, I would say. You should feel even more obligated now. Also, consider sharing things around about your publisher's other books and authors. Even though I probably won't be putting many books out with other publishers - I have plenty of collections, novellas, and novels coming out through Blazing Owl Press - I will still help to promote them: books that I'm in as well as those I'm not.
By promoting your publisher and fellow authors, you will be promoting yourself as well. Simple shares on Facebook and retweets on Twitter go a long way, and they're not spammy. Be a good author. Help everyone.