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