One of the best recommendations I can make for fellow writers is this:  critique the stories of others.

We all take for granted the advantages of having someone else read our work, from big picture review to catching typos that our eyes just skip over, but even if you never submit a story to a workshop or post on a forum in turn, the process of critiquing can be immensely helpful to your own writing and editing.

First, it helps hone your critical eye.  Picking out what elements you like or don't like in a story and - even better - trying to analyze why helps you be aware of flaws when you return to your own work.  Read a tale that involves an act of deus ex machina, and it might bring your attention to a badly used coincidence in your novel.  It's also a "safe" place to notice these things, when you don't have the personal attachment of it being your keyboard-borne baby.

Second, it helps you separate objective and subjective issues, especially if you read outside your preferred tastes.  Is this battle scene and its gore over the top, or are you just not the intended audience?  What about an unhappy ending - is this cheating a reader, or do you just hate them on principle?  This kind of perspective is useful to have when, inevitably, an editor's rejection bounces back to you with comments, and you have to decide whether or not they have a point.

Third, the act of writing the critique improves a different set of writing muscles.  An effective critique discusses the story subjectively and without directing its suggestions straight at the author - where comments can too easily be taken as attacks.  Instead, a good critique focuses on how the reader reacted to the story, without much attention for the author.  (Comments like, "English must be your second language," or even, "I assume you're a native, because your grasp of (X) culture is ..." are landmines.)  This leads to using "I" language instead of "you" language, which puts people on the defensive in any context, much less one so artistically personal.

Of course, reading a set of critiques is a skill of its own ... but that's another topic.