If you are in college, you need to locate the people in your Department/school who are involved in research. You can start by the web page(s), checking faculty publications. You want somebody who publishes regularly and, especially, with students. Also, check who has external funding for her projects (NIH, NSF, etc.) This is also a good policy if you are in high school and trying to find a good school to attend.
Once you have located your target, you may want to contact and ask those of his/her students currently involved in research projects, particularly if your school has a graduate program. They will give you the best insight and advice. Applying for work-study positions at the Department, or simply volunteering to work at the labs (even if it is cleaning around or serving as an attendant to a graduate student in her thesis research!) is always a good idea too.
As for your research subject, you more likely will need to start helping with their projects. This will help you to learn the trade. Try to read everything related to the subject, and hopefully, with time, you will be able to come up with your own interest within that field and start your own projects.