In forming your character, the basic formula would be

personality + occupation + family background = character

You need to be very specific on these things especially on family background because this can bring out so much from your character. If your story speaks only about the shallow parts of your story (boy meets girl, etc.), it tends to become boring and does not strike the audience the same way with what you were expecting.

As for personality, your character can be as normal as any person could be. It's just that you have to make her natural yet unique. Don't go for mary Sue (I'm sure I've told you this before).

Occupation. Ah, this topic is something I'm most interested in, to be honest. I've seen a lot of students running around AFF most of the time. Now, I understand the most of you are on the age of 12-16 or something near that range. It would be even better if you assign a certain occupation/job to your character to get out from this "school life" story everyone seems to be rooting for these days.

To do that, list 10 jobs you are most interested in doing when you grow up. Research about it if you think you're not familiar with it. And after that, you can create a very realistic and natural character without being similar with other stories' main OC.

List of jobs you can use:

Photographer, Secretary, Gym teacher, waitress, car wash employee, construction worker, translator... and the lsit goes on.