In most places, you can become an EMT in a single semester of school at your local community college. Although it's one semester, it's usually divided into multiple classes (even though you're required to take them all at the same times, usually have the same teachers, and the same classmates). For example, at the college where I teach "EMT Class" is actually 5 back-to-back classes: EMT Fundamentals, Medical Emergencies, Trauma Emergencies, Special Considerations, and Clinicals. If you contact your school's career counselor or your local community college's advising center, they can tell you exactly what they call their classes, how to enroll, and how long it will take.
If you're looking for things you can do to prepare, you will be required to be certified in CPR / AED prior to becoming an EMT. So, you can start with what we call a BLS (Basic Life Support) Provers class. You can also take health, biology, or anatomy and physiology classes while you're still in school to help you prepare; these are not required to become an EMT, but it will make EMT class easier for you when you get there!
Julia recommends the following next steps:
University of Pittsburgh: https://catalog.upp.pitt.edu/preview_entity.php?catoid=5&ent_oid=137&returnto=66