That's good advice. I noticed from your other posts that you have a PhD and are now pursuing a MD.
So you seem to be a good person to ask this question of: apart from doing wet lab research, what other experiences - particularly clinical -- should I seek out to help me make that call as to clinical work v. research.
FYI, I've had about a year and a half of experience with wet lab research that ties directly into potential new cures for a certain type of pernicious disease. That specialty is very academic medicine oriented. My clinical volunteering experience has been limited and entirely related to a different type of specialty.
You will have to adjust your experiences based on whether you are trying to apply for MD-PhD or MD only.
While MD applicants don't necessarily need too much research experience, MD/PhD applicants focus very heavily on research. It will be important to show heavy involvement in at least one project, with authorship on a publication being a good indicator of this. That being said, authorship does not guarantee admission into a program nor is it the best indicator of who will be a good MD/PhD student. For this, you will absolutely need a stellar letter of recommendation from the highest authority in your lab (usually the PI). The strong letter of rec from a PI is as important as GPA and MCAT for MD/PhD prospective students.
Because research is very time intensive and often runs at odd hours depending on what your project needs, you may find yourself not having much time. This is to be expected, and a successful MD/PhD applicant does not necessarily have as much volunteering because of how much time they spend in the lab. That being said, you will want to cast a wide net when applying, and you will likely want to apply to both MD and MD/PhD programs to increase your chances of getting into something. Not having as much volunteering/clinical experience won’t hurt your chances of getting into an MD/PhD as much as it would hurt your chances of getting into an MD program.
While getting some sort of clinical job is good for MD applicants (EMT, CNA, MA), it is not the only way. Getting a clinically related job will give you a lot of clinical hours, but for an MD/PhD applicant, the research is more important. So the best thing for you to do is continue working in your lab (if you have good relations with the PI and have confidence you can get some sort of leading role in a project eventually in addition to a strong letter of rec) and volunteer (both clinical and non-clinical) on the side.
Ideas for clinical volunteering: hospital, free clinic, hospice, etc.
Ideas for non-clinical volunteering: anything related to an underserved population (migrant workers, homeless, and people with disabilities)
Clinical research experience is not as valuable as basic science research in applying for MD/PhD, nor does it substitute for the need for clinical experience. Clinical research may get you published faster, but for MD/PhD you will want basic science research experience no matter what.
No matter what you choose to do, make sure you can stick to your commitments and don’t spread yourself too thin. Long term commitment in a few activities is a lot better than sporadic, short-term commitments.