Be Creative: Most people read other fanfics before they write their own, and sometimes those are the only ideas you have to for reference. Before long, you're tempted to use an idea or two straight from another story.

DON'T DO IT!

Fanfiction or not, this is plagiarism, and a very serious thing. Someone is always bound to find out. No one wants to read a story they've seen somewhere else. (And we've all seen what some people will do if they discover this fact.) We've seen some cases of direct plagiarism from copyrighted books, and if you have any moral consciousness about you, stay away from anything of the sort. So even if it takes you a month or a year to come up with something all your own, it's all worth it.

Clichéd Ideas: I hate to say it, but most SM fics are grouped into one cliché or another. It's hard to come up with new ideas, especially if you've only seen certain episodes (i.e. the R break-up) There are so many of these out there, that it hurts to read them.

First season fics used to be really cute, but now they all consist of the same formula: Usagi + Mamoru + matchmaker + compromising situation = instant passionate combustion. While I like WAFF and all, this is too much. Like Chibi-Usa on caffeine.

Editing: Even if you write everything in Notepad (or WordPad, or any other processor program out there) make sure you take the time to check it over for any mistakes. Don't just type it up and send it to a hundred archives the minute you finish it. No one will read it if it's full of grammar and spelling mistakes. It takes five minutes to use the spellchecker on it, but even then, you have to be careful because some things might escape even the most watchful eye. ^_~

Have someone you trust read it over for you so you can get an honest opinion, plus a quick proofread of things you may have not caught earlier. The same goes for word wrap. The custom wrap is 70 characters per line (give or take a few depending on your preference) but please wrap the sentences so you don't have to scroll forever to read one line. A lot of people won't bother to read your story if it isn't wrapped.

Mixing Versions: We all know how troublesome this can be. For example, more and more people have seen the subbed version of Sailormoon (or at least read about it), and prefer to write in that genre over the dubbed version. (If you're looking for a purist vs. dubbie debate, you won't find it here.) My point is, stick to one version when you're writing, unless you have an absolutely darn good reason for doing so. If you do, make sure you explain yourself beforehand.

Avoid Mary Sue: If you don't know who Mary Sue is, I suggest you read up on her before beginning a new fanfic. Mary Sue is a new character (usually heavily based on the author themselves) who is all around perfect, sometimes introduced as the new villain in disguise, or invented to get the token male's attention. Oh, and everyone ends up hating her. So I would suggest resisting the Mary Sue urge.

Do Your Research: Before you attempt to tackle fanfiction (or any other subject for that matter) look up your subject first. Try to get to know your characters before you stick them into a situation. Some of them have very complex personalities, and it's not that simple to throw them into a fanfic and expect them to work out perfectly. Get into your character's mind and try to think what they might be thinking, according to their strengths and weaknesses.

Above all else, HAVE FUN! It's not about the number of reviews, or about the attention you might receive. You're writing for yourself. You shouldn't be writing if you don't enjoy doing it in the first place.