UPDATE:
Hey, I recently found out the following link doesn't work anymore. I have decided to leave it in, just in case it ever does come online again. If you can't do the test below, I still recommend searching for another test, just to get a second opinion.
The link below is for an excellent online Mary-Sue test.
http://katfeete.net/writing/suestart.php
If you're determined to make 100% sure that your main character isn't a Mary-Sue, it might be worth taking time to do this test. Trust me, it's really good and goes into a lot of detail about how to lower your characters Mary-Sue count.
This is not mine by the way, I don't own it. For copyright reasons I figured I should add that.
YOU ARE READING
Anti Mary-Sue Character Guide
Non-FictionHere is just my list of tips of how to avoid creating/writing a Mary-Sue character. Take them as you wish. Greatest Achievements: #1 in non-fiction!!!