Keeping abreast of fiction and poetry markets is an ongoing challenge where Duotrope can help
You get an idea of the opportunities from a comment in Duotrope's August Month-In-Review: "Last month, we added 121 new listings and made 2,704 market listing updates." Bookmark the site and visit weekly.
Read each listing carefully, thinking all the while about unsold manuscripts waiting in your files. Also, jot ideas on index cards, to ponder and develop later.
Save yourself lots of frustration by scrolling down to check out Fiction Markets that have Temporarily Closed to fee-free submissions.
Don't overlook the wealth of information you'll discover by scrolling to the bottom and reading
New Editor Interviews, and Recent Responses -- you'll need to follow links, but you won't be disappointed, only wishing for more time to become better informed about markets where you strive to be published.