I think it is important to have at least some idea of what you are interested in before diving into research opportunities. Broadly speaking, if you are interested in psychology, you should volunteer in a psychology lab. If you are interested in neurobiology, I would suggest getting some coursework done before applying to volunteer in those labs.
Also, don't be intimidated by emailing the PI and/or lab manager of the lab. Explain your experience, your interests and your goals both within the lab work experience and in your academic career.
Best of luck!
This professional recommends the following next steps:
- Think about what you are broadly interested in
- Find labs at your school that relate to your interests
- Compile a resume and/or cover letter
- Email! :)