How To Name A Mary Sue
1. Stick with the tried and true.
Sakura. Serena. Arianna. Raven. They're used over and over (at least in the past twelve months) because they're classic. Sure, you may never have met anyone with these names in real life, but in the magical land of self-insertion, there are more Sakuras than Sarahs and more Ravens than Elizabeths. There's always room for one more.
2. Mix cultures violently.
It is safe to assume two things: that the vast majority of your audience will be American, and that all Americans have names like Fleurette Feinstein and Tomoko Meriwether. Nobody will blink if you name Harry Potter's long lost twin sister Esperanza. If anyone does object, you can insist that your character's mother gave her an exotic name just because she liked it. After all, it's a good enough reason for you, right?
3. Pull a string of syllables out of your hat.
Only the truly anal subscribe to the old-fashioned theory that people's names and meaningless gibberish are two different things. Consequently, if it occurs to you after a dose of cough syrup that your heroine's name should be Rhyntoliwen, Merydia, Bryndei, or Benadrylle, go for it. If people can't figure out how to pronounce it, they're probably not smart enough to read your story anyway.
4. Steal.
A good writer gets ideas from everywhere, and a good name is hard to find. When stumped for a suitably gorgeous name, raid your bookshelf or anime collection. It's much simpler to name a character Arwen, Guinevere, or Rinoa than to rack your brain for something original -- besides, who's going to notice?
5. Appropriate a vocabulary word.
In days gone by, our ancestors named their children things like Patience and Charity. This probably has nothing to do with the fact that they wanted their kids to grow up patient and charitable, so naming your pagan demigoddess Trinity, or your blonde, blue-eyed heroine Ebony, is a perfectly viable option. If you choose a word that has something remotely to do with her personality, you're simply being extra clever. Names of flowers, jewels and arbitrary mythological figures are good choices, as are nouns ending in "y", such as Destiny, Rhapsody, Vibrancy, or Perjury -- wait, maybe not that last.
6. Buy in bulk.
One polysyllabic name is good. Two is better. Six, it stands to reason, is fantastic. When your beloved character introduces herself as "Lady Raven Magnolia Amberyl Sparkalita Trysten deMoyne", you can be sure that she'll make an impression. It need hardly be said that none of the six or seven names have to be thematically, linguistically, or otherwise related. Variety is the spice of life (see #2).
7. Dare to be different.
Continuing this thought, the best way to make your heroine stand out from the crowd is to give her a name that does not remotely resemble those of the people around her. An elven princess of Middle-Earth, for example, is much more memorable if her name is Jessica.
8. Have a cutesy nickname in mind.
Nothing says "I have completely fallen for your pretty cerulean eyes" like an affectionate pet name. Accordingly, you should consider choosing a name that can be shortened by the character's love interest and intimate friends. Obviously, this is easiest if the full name is four syllables or more. Another option is to choose a completely unrelated nickname such as "Kitten", "Shadow", or "Sparkles".
9. Speal and pronooncee kriaytivlee.
An excellent way to show off your creativity is to come up with new and different spellings for your chosen name. Myranndah, for example, is much more original than Miranda. Alternatively, think up a prettier way to say it, and add an Author's Note to your story explaining to your rapt audience that it's pronounced "my-ronday".
10. Imitate life.
When all else fails, you can always name your heroine after yourself. If nothing else, this ensures that nobody can say it's not realistic. Also, your readers will instantly be able to recognize how important she is to you, and will refrain from calling her a big fat Mary Sue.