I'm writing a novel called The Phoenix Within and its about mainly a half phoenix half human female. I'm thinking about making her a fire elementalist but I dunno. she has short dark red hair with yellow eyes, she is full breasted but going on from there is the hard part of as a writer.
Right, well it doesn't seem like you have a lot to go on there. An important thing to realise is that the setting of the story influences the character; I'm assuming since you mentioned an elementalist that it's within the fantasy genre, but is it high fantasy/low fantasy? What's the setting, e.g. what's going on around her, what's the state of this world that she's in, is there a dictator, what is there that creates potential conflict? If all you have at the moment is what you've posted above you need to seriously think about putting a lot more depth into it.
It is true that going on from there is the hard part (well, one of them at any rate). But it's also the part that makes the story uniquely yours. You're better off not having people come up with these elements of your stories and characters for you.
If you go with anything using the four elements, make sure it's not cliche or shallow. Really work hard to make it your own. Also, you could stop by the Character Development Clinic in Word Games and I'll make some questions for your MC.
This. I don't particularly care what she looks like. I don't describe my characters much, either. Answer me this: Who IS she? What is her personality? Where does she come from? Where is she going and why? And what is motivating her? Write some scenes involving her. See what she does in certain situations. That should help you understand her better.
If you are just developing your character, then their physical attributes are the last thing to concern yourself with...unless they have bearing on the story. And even if they do, they are mere reflections. But after the characters have been settled, I think physical attributes have their use. for example: "Hey, blondie!" I/He/She spun and found Nargh, Captain of the Royal Guard, had blocked my/his/her escape. This gives the reader a hair colour, a possible nickname, a possible association to each combatant. It might not seem important, but if you draw in your characters with too general of a description, they all become one in a reader's minds-eye. I have read stories without a physical description and they read fine. Had I known a bit more about the build/height/etc, perhaps I would have pictured their characters in better detail.
I'm not trying to be rude here but this doesn't sound promising. This is nothing that hasn't been beat to death by nickelodeon cartoons and/or anime. Why does she have to have yellow eyes? Because she controls fire or just because it sounds cool? It doesn't sound like you have many plot ideas at all. Maybe it's just me but usually ideas just come to me and I don't have to think too hard about it, it just comes naturally considering the characters I have in mind. What you have written sounds like it's been done too often. A girl has to train to hone her powers, learns of her nemesis and vows to destroy him and so on...
I will just say this I myself started off with a character. I used the character in most of my short narratives for years before settling on where to put him. It took a long time to develop a story around just one character but you can do it. The key is just to understand the character. So as everyone is saying you need more first. Develop a personality and some other aspects and just like a car take the charater out for a test drive. You may find the character doesn't work in the story you are trying to tell anyways. For me the main character was pivotal but that was because we are bonded. In a way my main character is me and I needed him developed before I went on. If you have the time by all means try the character route first but the thing is it WILL take time unless you are leaving us with a bare description and no details of the world. My guess is the later of the two as why would you have a half pheonix human hybrid if you have not thought a bout your world to begin with. I also know many writers that carry around all sorts of characters till they find a use for them as well. So develop the character more if you haven't and whether you hate or love the final character do not forget about them as they may become relevant later.
Cool, im writing a novel series with a similar name. But don't worry, it's a totally different plotline then yours. Well, my main charcter has phoenix powers but he's isnt half and half. He is more of a half god, half human i suppose. But at-least my plot is different and my main charcter has a different appearance. ha.