Are you asking about doing research in medical school or in general/between now and then? In general, I can say that it's a numbers game from the applicant's perspective. It's kind of like getting a date for a guy. You'll get rejected but every now and then, you'll get a bite. If I interview a few undergraduates for a position, I'm going to take the one with the most relevant experience and/or the most motivated/passionate. If you aren't experienced, then you need to make up for it with passion. Why do you enjoy the research I'm doing? Why do you want to do it? Are you familiar with the recent literature we work with on a daily basis? Do you show initiative and creativity in solving problems? If you can check all of those boxes and get it across, you put yourself in a great position even without research experience in the past. We realize that everybody has to start somewhere. But it's hard to justify taking on an undergraduate who we have to teach everything compared to another undergraduate who can hit the ground running and be productive on our projects unless there's another compelling thing setting the former apart. That's why that "other stuff" is essential for tipping the balance in your direction.