Every veterinarian gets asked this question, so here are the steps taken by most pre-veterinary students. Many students know from a young age that this is what they want to do. I like to encourage students to take advantage of job shadowing opportunities and R.O.P. to investigate this profession further.
First of all, spend time with animals! You are getting comfortable reading animal body language and that will be crucial later. The better you can communicate with your patients (and their humans), the more effective you will be.
Academic success is important to achieving your goal, so start good study habits early. You do not need to be a mathematics genius, but you will need to learn math through first year calculus: Also physics, chemistry, biochemistry, zoology and statistics. Take as many English, math and science courses as possible in high school so you are well prepared for college undergraduate courses. Your college grade point average will need to be 3.6 or better for many of the top veterinary schools such as U.C. Davis. You will also need to take the GRE (graduate record examination) before applying to veterinary school.
You do not need to do all of your undergraduate work in a four year school-junior college is fine for your general education courses; just make sure your courses will transfer to your four year school and will also be accepted as prerequisites for veterinary school. Common undergraduate majors are biology, zoology, and animal science.
In addition to doing well in school, you will need to spend many hours volunteering for or employed by a veterinarian. Try to get experience with as many different types of animals as possible. Veterinarians and professors will also need to provide you with evaluations and letters of reference, which the veterinary schools look at carefully.
All told, you will be spending four to five years in undergraduate college courses and then four years in veterinary school. Some students get a masters or pHD prior to entering veterinary school. Usually, the first three years of veterinary school involves course work, laboratory work, and "hands-on" learning, followed by a senior year of clinical rotations and national and state board examinations.
Many new veterinarians will spend an additional one to four years acquiring advanced training. Other will go directly into general practice. It's a long, hard road, but well worth it!