As far as my journey, there were plenty of sacrifices, but all worth it now that i'm finally ready to apply (filling out secondaries now).
When I met with the admissions office to map out my plan, these were the things they stressed would add to my application:
1) a recent record of academic excellence (especially in science classes)
2) patient contact experience
3) goodwill works (volunteering, experience working with disadvantaged groups)
4) bench or clinical research, the closer to clinical applications the better - for instance, working at a marine biology lab would be less impressive than say a lab working on aids, diabetes, arthritis, etc.
5) a good MCAT, shoot for 11+ on each section
6) physician shadowing
7) experience in a hospital (volunteering, working, shadowing, etc.) this one kind of confused me, but the admissions office said they often notice it when a applicant hasn't had significant time at a hospital. Many applicants feel they've met their patient contact requirements by volunteering at clinics, ER, doctor's offices, nursing homes or being an EMT. But the admissions guys told me that because the bulk of your clinical training as a medical student will be in hospitals they want to know that you've taken the time to do your homework and learned exactly how a hospital works and various roles of different specialties and support staff. One guy put it to me this way, "would you want to accept a guy into the seminary, just because he liked church, hung out with churchgoers, but never actually went to church?"
As far as the sacrifices I made, I took a 40% pay cut to get a secretarial job at a hospital, but used it to segue into a nurse's aide job at a cancer hospital. But that was offset by the tuition benefits which let me take two classes a quarter for free. Had to learn to budget alot better with the little money I'm making now, but I look at it as good practice for during those lean years as a resident and fellow. I've also had to learn to manage my time better (my wife and I still fight about "us" time and our lack of it). It's not just taking pay cuts that hurts. Working full-time while taking classes isn't the only thing on your plate. You have volunteering, studying for the MCAT. I've volunteered at a hospital, been a volunteer research assistant, all while working 40+ hours at a hospital, taking 2 classes a quarter. And still had to find time to shadow physicians and do my own personal research on medical issues and the latest medical research. It ain't easy and every now and then you need to just get away and do something not "medical". I play the guitar, and quite badly I might add, but I love it because it has absolutely nothing to do with my career, and I'm allowed to suck at it.
Oh yeah, here's another tip. Starting now, start reading the Health & Science Sections of every major newspaper in the country. I used to peruse the websites of Boston Globe, NY times, LA times, Houston Chronicle, etc, about once a week, to read articles about health issues and the latest research. It will really give you the grounding to speak intelligently about a range of medical issues. When I shadowed an attending earlier this year he was so impressed by how much I knew about universal healthcare systems and health issues in general that he offered to call the admissions committee where he's a faculty liason on my behalf. And honestly, I was really just expounding knowledge I loosely got from reading newspapers.