Take out a subscription to a professional writing magazine. Recommend Writers’ News/Writing Magazine and, for women, Mslexia. All kinds of reasons for this tip but to name two - entering competitions gets you used to having to meet a deadline and you find out more about the writing world, including how other authors work. The latter I always find interesting. And subscriptions are an allowable professional expense too.
Writing What You Want To Write
Write what you want to write. Anything else will seem false. Fashions come and go in publishing as in anything else so it’s pointless trying to write in a subject or genre that sells now. By the time you’ve a manuscript ready, the market will be focussed on the next big thing.
Beware the Charlatans
Be aware, as in any industry, there are charlatans. Not only can the writing magazines alert you to these, they can point you to websites like Jonathan Clifford’s anti-vanity press site for further information.
Planning Your Characters' Lives
Have you got your characters’ lives planned out? It’s not a case of knowing every last detail but do you know what’s going to happen when? Do you know what your characters think they’re going to do with their lives (which of course doesn’t have to be what actually happens)?
Outlining and Reworking
It pays to outline your short stories, if only a couple of lines, before writing them. I’ve found it saves me wasting time dithering on the “what do I write next” dilemma. Do rework rejected stories and send them out elsewhere. You’ve got nothing to lose trying!
Write First, Edit Later
Get your story down on paper first before you even think about editing. Some authors do edit as they go but the disadvantage to that is it can take a lot longer (will you ever find the perfect sentence?) but if you get your story down, you know you have something to work with. Do put your story or novel aside for a while after writing. It’s normal to think you’ve written total rubbish just after finishing your tale! Give it some time and you can read it with a “clear” mind and sort out what really is rubbish and what isn’t. I can never judge my work objectively directly after writing it. !
Feedback
I’ve not joined a writers’ group. Some find them helpful, some don’t. But it is useful to get someone you can trust to read your work. Very close friends and family aren’t objective enough. Equally I have found feedback from sites like Shortbread Short Stories and from the Winchester Writers' Festival invaluable. If you pay for feedback (book doctors and so on), ask around and see if others recommend them.