How Not To Write A Mary Sue
So, what is a Mary Sue? It is used as a form of criticism in literature and refers to an idealised and somewhat "perfect" character that appears to have no flaws or if they do they are so limited that all the "perfect" characteristics overwhelm them making the character "flat." Mary sue often refers to a young female protagonist and male "Mary Sues" are often called "Larry Stu".
From my experience most Mary Sues are written in non-published works usually by young writers especially in fan-fiction. However there are a few Mary Sue writers who are actually published (sadly). It shows a deep lacking to create perfect characters unless it's done for satirical purposes.
So why should you avoid writing Mary Sues? Simple, perfect is boring!
We don't like perfect, we don't want perfect! Ask anyone in a relationship to list the positives traits, charms and idiosyncrasies of their partner and I guarantee at least one will be something that is weird, annoying, bizarre etc. Whether it's a crooked smile, the gurgling laugh, the snoring, the clumsiness or what, there will be something in the list that has been seen as a charm that others may see as a negative characteristic.
Next, nobody IS good at everything! There are not wonder people who are smart, funny, sexy, charismatic, nuclear physicist who speak 18 languages 4 of them dead and can read minds, hot wire a car, hack a computer, fly every type of aviation vehicle ever made all while playing Beethoven's 5th blindfolded with spoons!
It is crap and it reads like crap! So why do people write them?
I am sure there are 100s of reasons, one that I have seen is that the writer has an esteem issue and would love to be able to do all those things so throws them all into one or two characters. Result snoozefest.
By giving a character all these great skills and charms and talents they become under developed as a character. After all, people evolve, grow, change and adapt, if you make a character perfect there is nowhere for them to go.
So how do you stop from writing this? Firstly do NOT make the character you. A writer puts themselves into almost every character they write. Develop your skill by not putting too much of yourself into characters they are not you. They can be extensions of yourself, exaggerations of a part of your psyche but they should not be you.
Second plan your character in pieces. The pieces are Physical, Emotional, Mental, Skill/Talent and Knowledge. Take each one of these pieces and decide about the character. Think about them now and what they will develop into. If you write a character over several books or over a long story, they will need to develop.
If your character is young such as child or teenager you could write their physical looks realistically. After all children are often awkward in their bodies, as they grow their limbs can look almost gangly, there can be what is referred to as "puppy fat", they can get spots etc. Their faces and bodies will show a little of what they will be but their features will change as they age. Rarely do you get youngsters who never show any of these and are crowning beauties right from infant to adult. So don't write that!
Emotional and mental are two pieces that change with both age and experience. Characters can become embittered or enlightened. They can be abused and so end up with trust issues and emotional scars. They can experience acts of mercy and redemption that may turn a darkening belief in the world into something positive. The gender of the characters also needs to be considered when dealing with these two pieces (though be aware you don't automatically stereotype your characters emotional and mental reactions).
With skill and talent whether it's re-building a computer from scratch or flying a helicopter give your characters the skills and talents they require for their character. E.g. if your character is a fighter pilot then being able to fly is obviously necessary, you can even have them as the best fighter pilot but think about developing that maybe they are arrogant because of their ability, which isolates them from other characters or maybe they try and hide their abilities because they are worried they WILL be isolated etc. This allows you to link skills to emotional/mentality.
Also, give your character scope to develop. Their skills, talents and knowledge should change whether this is to increase or decrease. Don't get into the expected mindset that states all these need to increase. Imagine a sharp shooter character excellent ability, what happens in his life maybe he loses his daughter, turns to drink or drugs or maybe just can't stop seeing images of her wherever he is, now he's losing his ability, unable to focus this is a change, a development to the character. If a character has great skill, you could take it off them or dull it down.
How about giving your character a vice (please note this should not be your ONLY negative trait for a character, one single vice amid a lot of super-great abilities/looks will still read bad! But a vice or two can be developed and will help you find new conflicts to overcome etc) There are many vices and some things may not seem to be vices such as pride, trust these in extremes can be considered vices and affect a character.
By thinking about your characters, their histories, experiences, mentalities and plots can help you develop them into something more than a perfect yet one-dimensional character that people will find dull to read.