Writing Style

I have been mentioning this topic for a while, so it is time I do a post on it.

Obviously, writing style is important. A distinction should be made, however, between writing style and grammatical correctness:  Like a Tide Laundry Detergent commercial mentioned, "Style is an option; clean is not."
Similarly, WRITING STYLE is something that differs depending on who you read, because everyone's voice is different; even if Barnes and Noble classifies an author under specific genres or styles, the Vampire Kisses series is not written in the same style as the Twilight series, though they are both vampire romance novels.
However, GRAMMATICAL CORRECTNESS is ALWAYS MANDATORY, unless you are writing a fan-fiction that you intend to be a bad thing on the Internet.  Grammatical correctness needs to be a requirement for any published novel or story, regardless of whether or not it was self-published.  Small things that are easily overlooked are excusable if they are few and far between; constant misuse of words and/ or misspellings SHOULD NOT BE TOLERATED.  Do not rely entirely on your computer's Spell Check, because it can be faulty - sometimes it will tell you to switch around a word or two that may affect the meaning.
I would like to point out that the phrase "I'm just a bad speller" is never an excuse.  If you ask your friends to read and edit your writing (make sure your friend is an English major or at least has some interest in literary quality), you can easily catch any errors.  Additionally, though you should BE AWARE of Spell Check, that does not mean it is your enemy.  Though it can be annoying at times and sometimes it can be wrong, it is frequently correct, and you should note when it is telling you something.

Writing style in and of itself is something that can be interesting to study.  Though it is not entirely the same thing as a writer's voice, the two are very similar.  The writer's voice is how you hear the narration as you read it; the writer's style is how the author writes it.  Style can be genre-specific (but not always), whereas voice is always subjective.

Really the only way to improve your voice and figure out what sort of style you want to use (even if it's one of your own invention) is to practice.  So go forth and write! :)