I believe that my M.S. absolutely, 100%, completely, and totally got me into medical school. I don't necessarily mean the degree itself, but everything that came with it - the grades, the courses, the recommendations from faculty who viewed me more as a peer than a naive undergraduate student gunning for medical school, and the shadowing, working, and volunteering experience that I obtained while in graduate school.
After graduating from undergrad in 2001, I couldn't decide what I wanted to do with my life. I debated PhD, med school, Pharm school, Dental school, Vet school, and a host of other careers. I settled into a career as a research scientist in Seattle, where I remained for a few years. I then applied to medical school for the incoming 2004 class, interviewed only at 2 schools - UW in Seattle (I was in-state at the time), and WashU in St. Louis (I always thought it was strange, UW and WU, but I digress). I was waitlisted at one, and was ultimately rejected. I had a relatively average undergraduate record (3.5 total, 3.3 BCPM) and a 33R MCAT. I had minimal clinical exposure, some here-and-there volunteer work, but some significant research (which resulted in a couple of publications). As a back-up, I applied to the Microbiology and Immunology program at Georgetown (not the SMP), where I ended up matriculating. After completing my M.S., re-establishing Maryland residency, and working for a year, I applied (as a re-applicant) for the 2006 cycle. This time, I received 5 interviews, 4 offers of admission, and 1 waitlist (from which I subsequently withdrew after deciding on my state institution). Irionically, I was not offered an interview at either UW or WU that year.
At the time of my first application (for 2004), I had been out of UG for 3 years, had worked in research for that time, had a publication in the works, etc. The things that changed substantially between my 2004 and 2006 application were as follows:
1. I gained an M.S. My graduate GPA was a 4.0, which I believe helped offset my rather low-end-of-average undergraduate GPA. I know that it is calculated separately, but I still firmly believe that it made a difference.
2. A publication that had been "in submission" during the 2004 application cycle was published in Circulation, the journal of the AHA.
3. I received new references from several professors, mentors, and advisors at Georgetown who knew me extremely well due to the small nature of the program (which was quite a shift from my undergraduate courses, where there were easily 200+ people in a lecture hall at a time).
4. I spent significant time shadowing and volunteering at Georgetown Univ Hospital, and wrote my personal statement about an experience that I had while shadowing an ID doctor there.
5. I was able to spend more time working, which I also mentioned in my application as ECs.
6. I was extremely vocal, outspoken, and engaged in my coursework at GU, because I found the material fascinating. This certainly reflected in #3.
I think that the BIG clinchers for me were #1 and #3, with a smattering of #4 and #6. Whatever you do, DO NOT underestimate the value of your letters of recommendation. Graduate programs grant you the ability to be seen as a peer in the eyes of your institution's faculty. Cultivate this relationship with genuine interest, and you will get some amazing letters. I have not seen my letters of reference (I opted, as we all should, to waive that right), but I am certain that they say volumes more than any letter I ever received from my undergraduate institution, or even my ex-boss from my post-undergraduate research position.
Good luck. Let me know if you have any questions.
to you.
Honestly, your age won't be a problem at all; 24 is about the average for M1s at a lot of schools. I was 31 when I started, and even that is far from being the oldest. I didn't have to use any wrinkle cream either. 
