To become an EMT is going to take most of the summer for classes. The ride alongs or shadowing on an ambulance is good experience. To become an ED tech, you typically need an EMT-B certification and IV Therapy. On top of all this, getting a job on an Ambulance is not always easy and many hopsital's require experience to get the job as an ED Tech. I will say from experience that both jobs are great for learning medical... EVERYTHING, from trauma to minor care you learn a lot. I agree with OctoDoc, shadowing with doctors or others is really good experience and is going to give you a GREAT idea of what you are getting yourself into! Also volunteering with a hospital is a great way to get good volunteer time in, learn more about the clinical setting, and is a good way to get a job in the hospital.