In order to become an ultrasound technician, at minimum you have to obtain a 2 year education in an accredited institution and receive an associates degree. While this will be enough for you to work at most places, depending on your career goals and how much money you would like to make, you may furthermore advance your education by getting a certification as a medical sonographer. This certification is given by the American Registry of Diagnostic Medical Sonographers (ARMDS) after you pass the national board exam.
The schools themselves may have some prerequisites completed prior to acceptance into the program. These are general classes of sciences like biology/chemistry and medical terminology in some courses most of the time. If you meet these criteria you will be welcome to submit an application to be enrolled into the program. The selection process would involve writing an application, essay exam, background and reference check and an interview with the department. Going through each step, you will be graded and your overall score would determine your eligibility to be accepted into the program.

Your 2 year school education would probably be split into a year of theory and another year at a local hospital or an imaging center. Some schools have the necessary imaging equipment in place to under take the practice inside the school itself. Usually it is better to go to a hospital to get necessary experience under the supervision of an ultrasound technician. This is a priceless experience to work closely with a professional in your student life. The theoretical education includes anatomy, pathology, physics and courses on the body parts. Using the information gathered in the first year, you will be learning how to do actual scans in your second year.
As far as the ARMDS exam is concerned, they offer 10 prerequisites under which you are able to apply for the exam. First timers can select one of these to apply for the Sonography Principles test. Each of these requires an educational background, necessary scanning experience and documentation required to accompany these. Although these all sound scary, it is yet rather rewarding to get the certification. As this certification can lead you to a more successful career and working for a better salary.