You must have a college degree or higher AND complete a teacher preparation program. Teacher preparation programs are usually two-three semesters long. A few 4-year baccalaureate programs allow you to complete course work for your baccalaureate degree and credential at the same time. These 'blended' or "integrated" programs are generally more intense than traditional programs, but allow you to become a teacher faster. Browse the Find the Right Preparation Program for more information.
Each of the three teaching credentials: elementary school teaching, middle/high school teaching, and special education have their own requirements. There are also several paths you can take to earn your teaching credential. The three main choices are explained in the "Paths to a Credential and Basic Requirements" section.
It is very important that you speak with an academic advisor throughout your college career so you can know exactly which courses complete the teacher credentialing requirements.