It's pretty obvious that usernames are the most important part of the forum. Well, second-most-important. Sporks are the most important. Anyways, it makes sense that there are some things that can't be in usernames, right?
One: You may have no vulgar words, or swear words, in your username.
Two: You may not change it left and right. You may change it ONCE per month.
Three: Please have some individuality. Make your username stand out, do that people don't think your someone else. Like, don't be Austin when there's an Auron. Or Vivi if there's a Vivi~. Instead, be something that stands out. Like Nobleslug, or .Death_Angel, Chibi_Kitty x3, etc. This is so you are reconizeable easilier, and people don't get chat messages mixed up.
Anyways, just follow these three guidelines when making your username.