Answer:
You should be able to communicate effectively with children and people of all ages. It's extremely important that you can share knowledge with the age group you are working with in a way they will understand and absorb, be able to communicate with other teachers and superiors, and be able to discipline children appropriately. You may be taught these things, but it generally comes with experience and confidence.
You should also be able to interpret and learn information, as this will be necessary when teaching and marking. I would say effective communication and confidence are the most important characteristics of a good teacher, it's also helpful to have a good sense of humor and other like-able characteristics, children who hate their teacher are more likely to mess around, not enjoy themselves and not want to learn.
Good spelling skills might also come in handy?