It can be tough submitting your writing for publication, but don't get discouraged if you keep getting rejections. Editors and publishers have different likes and dislikes. You should also keep a record of your submissions.
David M. Harris, who "has taught English at Vanderbilt University and elsewhere," according to the description of the following video, shares this advise to whoever aspires to be a published author. He also gives helpful websites. One such website is ralan.com, which lists science fiction and other speculative fiction markets.
Check out the video here: