To become a teacher in the US there are certain requirements that are required and often vary state by state. Most states require you to pass exams and have actual training experience in a classroom setting. In the United States you must also achieve a state license to teach in any of the public schools. If you plan to teach in a private school though, a license from the state is generally not required (although it never hurt). To get the teaching license you must apply to the state with your required education and a special committee revues and assigns the teaching license. The rewards for this teaching education can be a great experience.
However once you have achieved your teaching education and license through the respected state, your training and education does not stop there. There is always on going training and education that teachers must attend throughout the year. These classes and seminars are meant to help the teacher learn the newest techniques and sometimes over look techniques needed to progress in today's growing classrooms.
There are less requirements generally if you would like to become an early childhood teacher, generally this can consist of at least an Associates Degree in early childhood education and may require an additional state approved certificate. These teaching education associate degrees can be done through a community college and sometimes even done through online universities. These classes are the choice for most early childhood instructors because of the flexibility of attending class online. This works really great for stay at home moms that may or may not have time to attend regular classes.
In addition to attending classes to get your teaching education degree, you will often need to work side by side with another teacher in a classroom setting. This is often called a teaching assistant. These teaching assistants train in real world classrooms to gain additional experience before getting a class of their own. During this intern teaching time, the teacher assistant will gain the valuable training real time.