Last updated May 24 '12 at 13:59
You should attend a college with a psychology department. That department will publish degree requirements for students who want to major in psych. The degree requirements will usually list a certain number of courses that you must take in order to complete the degree, of which a certain number must be within the department, and a certain number at a sufficiently advanced level to merit your degree. For Psychology in particular, it's going to be some combination of psych classes and some statistics classes. Here's the Boston University psych department's explanation of required courses for their department: http://www.bu.edu/psych/undergraduate/degree/. You can google around to find psych degree requirements at other universities.
Keep in mind that in order for you to become a licensed psychiatrist, you're going to need to have a doctoral degree (usually a Psy.D.). That's about 5-6 years after you finish undergrad. That said, there are many other careers in the psych field other than being a licensed clinical psychiatrist -- with a master's degree (which is 2 years of education after you finish undergrad), you can do a number of other psychiatry-related jobs.
You're going to have to work hard on your writing and reading in order to be able to handle the extensive writing and reading required to do well in a psych program in college. It's quite challenging, but can be very rewarding!