Yalebound13,
My 2 cents: Don't pigeonhole yourself into the image surrounding one Ivy League university - my Harvard friends would be upset if they read this. Broaden your horizons. It's an important lesson to learn about psychology...there are no absolutes.
Your HS guidance counselor is the best starting point. And not to appear overzealous, but contact Yale's admissions department (as well as other universities).
If you are related to Yale alumni, then this may be a different story. Ask them for support. Learn the art of networking. Find a psychologist (the type you want to be: clinical, social, neuro, forensic, enviornmental, etc.) and try to meet with him/her to discuss the specifics of your desired career.
When I was in high school, I wanted to be a psychiatrist, and entered college as a pre-med math major (go figure!). When I finished undergrad, I knew clinical psychology was for me. It sounds like you have a general idea, don't be discouraged - just more open minded. Also, unless money is no object, save money by kicking butt now with grades, etc.

and look into scolarships or grants. I had a former coworker who loved her Yale degree, but was always so stressed about paying back her undergraduate loans.
I'm a huge advocate for volunteering, start volunteering now...and chose positions that will deepen your prespective on the human condition.
Good Luck!
