Creative Writing 101 will tell writers to "find their voice." An author's voice is a way to personalize their fiction, give it their stamp, and is a way to connect their novels even when they are completely independent from each other. Style, tone, use of language... all of these go into the ever-important "voice."
Something important for writers to ask themselves is whether their voice and their characters' voices are two separate entities. Fiction writers base characters on themselves all the time, and (as I mentioned, here) drawing from what you know can often lead to the best ideas. But where is the line between you and them, and how do you keep that balance?
As authors, your writing style comes through in descriptions, narration, themes, and types of characters you create. Those are what readers will associate with you when they recognize your name in bookstores. Once you create your characters and settings, however, you need to switch your focus every time your character says or does anything. Some questions to consider when making this switch:
- - What type of person is my main character?
- - Is this how I would react in this situation, or is this how my character would?
- - Do I use this phrase all the time, or can I allow my character to say it as well?
- - Given the context and tone of the novel, should my character act this way?
- - Is my character's name just my own name spelled backwards?
Mary Sues are frowned upon and ridiculed by your literary peers, but they are by no means deal-breakers. I can think of two massively popular novels out right now that feature these characters: Twilight and The Girl With The Dragon Tattoo. Mikael Blomkvist is essentially if Stieg Larsson was cast as James Bond (literally) and Bella Swan looks and acts exactly like Stephanie Meyer except omgeveryguywantsher, including the two hottest guys on the planet!
Before you say to yourself, "Yes! NYT Bestseller list, here I come!" remember this: These books are insanely popular because their stories resonated with bajillions of readers, not because these characters were particularly engaging, or even well-crafted. The characters who are memorable and more often discussed from these novels are Edward, Jacob, and Lisbeth - the ones who required more thought from the authors.
Next time you sit down to write, think about your main character. Is he or she just you in a different context? Hopefully you avoid the Mary Sue trap, but if you absolutely can't, is your story strong enough to back it up?