Warning: Long message.
First off, some of the posters in here are way too jaded...nepotism is everywhere but ordinary people can work their butt off and do well. I know several people that came from backgrounds where they were first generation and had no connections and just raw work ethic. Sure you'll find people that "stroll in a get publications" but, are you kidding me, the vast majority of the ones that get a lot worked their tail off. I too had a bunch of first author pubs and it was sheer and pure hard work with a lot of perseverence. My stuff was a mix of basic science, review, and short clinical papers (case reports, pilot studies, etc.). You are always juggling several papers at the same time. It does not take long for faculty to figure out if you are efficient as hell and they will feed you as much as you will eat. In fact, you will stand out and then they will let you call the shots for the project idea after they are satisfied with your work. No faster way to get publications than to become truly passionate about the work that you are doing...it's a snowball. I'm staying in academic medicine and it's not to so call "circle jerk", it's because it's a beautiful avenue of discovery...if you're too jaded to believe this, then I'm sorry that you feel that way. To boot, some of the richest people I know personally were academicians...I'm sure that's going to piss of the private practitioners that thought they had the financial part figured out. Academics gives you the front seat for entrepreneurial work and there are obviously ethical and unethical ways to do that. You have to have the social networking know-how though.
Secondly, it's clear that there needs to be more clarity on what a pub is. Pubs include everything like: oral presentations, abstracts, reviews, case reports, clinical pilot studies, book chapters, basic science manuscripts, survey based studies, epidemiological studies (retrospective and cross-sectional chart reviews as two examples), clinical trial manuscripts (BTW this is a true black hole for medical students because clinical trials, unless a pilot study, take a long time to publish...keep this in mind).
Thirdly, you get control of how quickly you publish when you take control of the submission cycle (agree with drizz). To do this, you need to find the right mentor who is not lazy. You also need to convince them with prior work that you are a hard worker. Find their publication list...if they publish a lot, it's pretty unlikely that they are lazy.
Fourth, most people count pubs because, guess what, bigger is better in their minds. You as an applicant should know that in research you should have a mix of high risk and low risk projects. It's not rocket science. The low risk projects should be stuff that is going to get published more easily while the high risk (basic science work for me) takes time but when it succeeds, you get an amazing paper out of it. No, I was not a PhD. For that matter, I find PhDs to be much more burnt out than MDs who work their tail off. I know several people that were co-interviewers for derm who published like mad and received 20+ interviews and matched with a cake walk. I applied derm and had a truly laid back experience with the match. A lot of people complain that it shouldn't be about quantity...well it is an important factor...there is no better way to show dedication than to repeatedly publish especially when you are truly interested in your publications. Everyone does clinical rotations and can do well in them. There is no better way to shine for the competitive residencies than to have the publication record that puts you over the top.
Fifth, you have to stay humble. The quickest ticket to not having success in research is to let you ego get in the way. The more collaborative you are, the more you will get out of research and the more people will want to work with you. I find it interesting to see the posts from people that are clearly jaded who talk about favoritism as if it is rampant everywhere...it's present but it's not the rule. There is no way in hell favoritism allows you to be a repeated first author...you will have to do the work to get that.
Sixth, starting early is key. I agree that taking the first semester/quarter to feel things out academically is important. This is why it is so important to go to a P/F school if you can help it. Grades do nothing but create more competition in an overly competitive environment. Most residencies emphasize step 1, AOA, and third year grades...Of course AOA may take 1st and 2nd year grades into account so you have to be ready. That said, if you know you would like to work with a certain PI, start early. Meet with them and let them know of you interest and more important why you are interested. The why is important and the how of approaching the PI/mentor is perhaps the most important.
Seven, don't just chase the bright lights in front of you. Just because you went to Harvard, UCSF, Stanford, etc, does not make you a better and more efficient student. Actually, I know a bunch of kick ass people from these institutions but I know a bunch of kick ass people from other institutions as well. The kool-aid version is that the average student at a top 5 med school is brighter than the average student elsewhere. What a great and useless line. Last time I checked, I wasn't planning on being average and last time I checked with patients, they don't want an average doctor. I know a bunch of people from top 5 medical schools that were also lazy as hell and wouldn't send any family members to them at all. Competitive residencies take from the cream of the crop and school doesn't make a difference. If you're cream of the crop, you'll make your path and find the right mentors to help you do that.
Like Drizz implies, everyone went into medicine because of someone or something that inspired you so you are biased coming in. Waiting until 3rd year to explore is a bad idea on so many levels. I think it's just bad advice and I never advise med students to wait until 3rd year to figure it out. If you have interests, explore early. If you wait until 3rd year, you will make decisions based on how you got along with your team rather than what the field may truly offer to you...you need to know that. Also, if you don't explore early, you may miss out on fields that aren't offered in the 3rd year, especially if you do have an interest.
Finally to answer the hypothetical question of isn't one good first author pub as good as having a first author AND a bunch of middle author pubs...yes, the one good first author pub should be counted the same and that a bunch of middle author pubs may not be that valuable. In fact, I love it when people talk about how they published in Cell when they were a fourth or a fifth author...BUT, rest assured that 10 first author publications will trump your one good first author paper (unless it is Nature, Cell, Science, JAMA, NEJM, etc), especially if there are a few good first author papers in those 10. Productivity and hard work are very desirable qualities and productivity in research is a very tangible evidence of this.
Guys, it's not rocket science. That said, no one said it was easy. That's why there are only a few that can put in the work to get there. But, it's not as hard as you think. Just so that you know I did not go to a top 25 medical school...I know that I had way more interviews than people that went to top 5 medical schools and I interviewed at their schools too. Yes, I have a social life and passionate hobbies/interests that are way outside of medicine.
If you prefer to be jaded about the process, then suit yourself. I realize that people have had a variety of experiences and some people really did have bad experiences and bad mentors...so I do respect the other point of view and my heart goes out and I'm truly sorry to hear about anyone that has been taken advantage of or screwed.