One way to sell more is to look beyond the obvious markets for your writing. Here are some examples:
1) Writing articles? Consider how you can re-slant your topic to appeal to different audiences. For example, to help promote my Your Writing Coach book, I'm going to pitch articles about how to write. The obvious market is magazines for writers, but I'm also going to pitch women's magazines for articles about how writing can heal emotional pain, and magazines targeted to older readers for articles about how to write memoirs for their grandchildren to read.
2) Writing short stories? Consider where the location or theme of your short story might fit in. For example, if your short story is centered around a garden, maybe a gardening magazine might consider publishing it. If they don't normally publish fiction, you could propose it as a special feature for their Christmas or New Year's issue.
3) Writing a novel? If it all takes place in one city (and doesn't reflect badly on it) tourist shops there might consider carrying it. Or if, for instance, it features an archeological background, maybe a museum might sell it in their gift shop.
4) Writing poems? As with short stories, magazines that normally don't publish poems might consider doing so at special times of year, like St. Valentine's Day, the Fourth of July, or Thanksgiving, if the poems relate to the themes of those days.
5) Writing screenplays? While the market for full-length screenplays is limited, often aspiring directors at film schools look for short scripts they can film as projects. You might consider getting your name noticed by writing such a short script--frequently, the best student films are shown at film festivals. You might even be able to fashion a short script based on one part of your full-length script (if so, make sure that you have a contract that keeps the copyright of the script in your name, not the name of the film-maker). I've just done this myself. The short film was shot but I've not yet seen how it turned out--I'll let you know.
As you can see, it's worth spending a bit of time brainstorming how to go beyond the usual in terms of marketing your writing. By the way, for more brainstorming tips, see my website, www.BrainstormNet.com.