1. You should have a lively imagination.
2. You should be able to write well. By that I mean you should be able to make a scene come alive in the reader's mind. Not everybody has this ability. It is a gift, and you either have it or you don't.
3. You must have stamina. In other words, you must be able to stick to what you are doing and never give up, for hour after hour, day after day, week after week, month after month.
4. You must be a perfectionist. That means you must never be satisfied with what you have written until you have rewritten it again and again, making it as good as you possibly can.
5. You must have strong self-discipline. You are working alone. No one is employing you. No one is around to fire you if you don't turn up for work, or to tick you off is you start slacking.
6. It helps a lot if you have a keen sense of humor. This is not essential when writing for grown-ups, but for children, it's vital.
7. You must have a degree of humility. The writer who thinks that his work is marvelous is heading for trouble."