1) Think of your character's personality first. Personality comes waaaaay before things like element or attacks. As a matter of fact, your character may look better if you fill out the personal questions first, and stats last.
2) Read through the other profiles first and see what elements/names are taken. We had 2 Sarahs at one point (we currently have a Mika and a Meka), and there's already 2 Ice elementals and 2 Darkness elementals. So please, make sure what you're choosing isn't used yet.
3) Background. Where is your character from? The SIM takes place in Los Angeles, so you might want them to be from there. Oh, and you may think that it might fit your character better to say that they've moved from [insert state you live in] TO L.A. to explain how they act (i.e.: the way YOU do in real life), but it isn't really that neccessary. After all, people are a big tapestry, your parents could be from Arkansas and that's why you have a southern accent or like country music.
4) Draw your senshi and send me a scan. If you don't have a scanner or just plain don't think you draw well enough, alter a regular Sailor Moon pic. Please, I'm not an art critic, anything you send me goes up! And if you get in, then Mina or I should be able to do one for you...but be forewarned, Mina's terribly busy and I have the scanner from hell. It'd be much easier if you just did your own. ^_~
5) BE ORIGINAL!!! No Sailor Uranus clones or "sisters that act just like her" or stuff like that.
And while we're on the subject, BE CREATIVE. Don't even bother submitting a 'Sailor Universe', a 'Sailor Star', a 'Sailor Earth', or, worse, a 'Sailor Chibi-[insert name here]'. Try to actually come up with something original.
6) Don't get too goofy or dark. I'm not sure if I want a Sailor Hugs-A-Lot or Sailor Hellfire. But I may change my mind.
7)Read through the preview form, I guarantee you'll find a very handy link there. And USE that link, don't just send an e-mail version of your application to Silva-chan, or worse yet me (Wynd), since it's not even my job to decide who makes the cut and who doesn't. Plus, it gives a very bad impression of you. (Much like branding 'IDIOT' across your forehead in large, bold letters would accomplish.)
8) A great place to learn better ways to create senshi is:
S6: Sailor Senshi Star Seed Source Shoppe
9) A great article on Sailormoon RPGs:
My RPG Qualms from Ginzuishou Plus!