| Winnowing the possibilties.
You are making a character here. You are not only writing a description for your character, you are making them here. The core of your character shall consist of what you enjoy doing, and a goal that allows you to do alot of that. You should think about what activity, like a career, is enjoyable to do. Keep in mind you will often be playing in a group, and that they thing you enjoy doing should be compatible with others. Most careers, and activities are compatibile but i find that people are marvelously creative when it comes to finding perfectly inplayable characters.
This career could be anything really. You could be an angel, you could be a computer nerd. However it is good to not be at the top of your field, otherwise there is no goal to reach for. You also need to make a goal for your character, keeping in mind that i will build the world around these items, making your goal involved and interesting, even if it is the impressive and complex art of crocheting martial arts. If you enjoy being a fighter i will create a world where you can be an active and interesting fighter. If you want to be a mage ascending the road to enlightenment i will design levels of truth that you can unravel, and a whole world to work through to get to your goals.
The goal and the career are the most important parts. However the next part is making a past for your character, you may want to keep a past in mind when you are making a goal and a career but the real purpose of making a past is to create dozens of loose ends for me to play with. Don't resolve things in your past, like if you tried to kill your father because he raped your mother, you failed and he is still out there. That gives me someone or something to bring into the present.
Lastly i want you to make a list of things which you want me to know. These things could be about the character, or about how you want me to setup his career, or what place you want in the world, or what age the world is in, the nature of magic or science, or scenes which you would like to see. Tell me if you would like to fight an army of deadites, or if you want to be fighting against a galatic empire. Things about your character could be that she is very lucky, or she has an overwhelming tendacy to get splashed with cold water - even in a desert. Tell me if you would like the RPG to take place in a world like the matrix, or in a world like trigun. The more you tell me about what you want out of the RPG the better i can build it for you.
Also, i would like to refer to a site which i think will help you make a three dimensional character: A Handful of Things to Thing About During Character Creation.
Once you get finished building the character tell me on aim, or email it to me. The world produced will depend entirely on what characters i get back. I will also be sure to help adjust your characters if they cannot relate to the others too greatly. I prefer the document to be in notepad, or word.