Writing is often thought of as a solitary processes.  However, there’s something to be said for working with other authors.  Recently, I teamed up with the authors of The Future Chronicles.  It got to #2 under Scifi Anthologies on Amazon, and is still sitting at #3.  Today, some author friends of mine who had released a bundle got onto the USA Today Best Sellers list.  It’s a tactic that I’ve seen work for other authors, as well.  Usually, you have to be invited into these sorts of things, but that doesn’t mean that you can’t go looking for them too and express your interest.  So make a friend, explore a common universe, and see what happens.  You never know what will come out of a little collaboration.