All cosmetic surgeons are physicians. That means they went to an undergraduate program and then went to medical school. You want to go to the best undergraduate program possible without racking up huge loans. That means that you want to apply to great colleges and then pick the school based on the total financial outlay you and your parents will have to put out. That's because when you get to med school, you will have a ton of debt just to get through. Most doctors graduate $100,000 in debt and some are over $200,000.
Most pre meds major in biology, chemistry, or biochemistry. There is no required major, though. You can major in French Literature and get into medical school as long as you take the required courses of General Biology (2 semesters), General Chemistry (2 semesters) General Physics (2 semesters), Organic Chemistry (2 semesters), English (2 semesters) Calculus (1 or 2 semesters), and sometimes statistics. It's recommended that you take 3-4 upper division science courses too though.
While in college, try to do lab research with a professor. Also, volunteer at a hospital. Some pre meds pick up an Emergency Medical Technician certificate in the summer and work on an ambulance. It gives them great exposure to the medical field while they are able to work a relevant job for pay (instead of in the school cafeteria for instance).
You'll have to take the Medical School Admissions test which cover the required courses listed above. The test is super-important so you will want to take a test prep course offered by Kaplan, Princeton Review, or another of the biggies.
When you do all of that, you're ready to apply to medical school. This is a good site to find out about medical schools:
http://www.aamc.org/medicalschools.htm So, you've got 4 years of college followed by 4 years of med school. But wait -- you're not done yet!
Next you've got a year internship followed by a six year residency. Fortunately, at this point you start getting paid. Not much, mind you -- around $35,000 a year, but at least you're no longer shelling out money!
This link:
http://www.facialsurgery.com/PPgresume.html is the resume of a plastic surgeon. You can see which colleges he went to (Harvard undergrad, U Nebraska medical) and the internships, residencies, and fellowships he went through.
Here's another Plastic Surgeon's biography:
http://www.surgery-plasticsurgeon.com/YourSurgeon.htm Good luck! Get good grades all around -- but especially in math & science. And always, always stick to your dreams!