Great idea for a topic, jacib. [An aside: jacib is even cooler in person than on these forums, if ya'll can believe it. We ate cheese fries.]
As a successful applicant this year, here are the things I think made my application work.
(1) RESEARCH EXPERIENCE: I had a boatload of it. I have worked as an RA for three years at a public policy think tank. The work was very relevant to sociology and the skills I gained will make me a really strong RA for some department in grad school. Particularly if you want to do quantitative work, the role of experience with programming and researching cannot be over-emphasized. I believe I would not have been a particularly special applicant without this experience. I may have gotten into a couple of the schools I applied to, but certainly not five. I agree with other posters who have said time off is important - working as an RA can be a great option.
(2) TAKE A GRE COURSE: It's a sad reality that GRE scores matter the way that they do. If you have the financial resources, take a course. It raised my score significantly. (I received a 730 on V and 760 on Q. Certainly people have higher scores than me on this forum, but I am confident that my GRE scores were never the reason my application was rejected from any school, and that peace of mind is well work $1,200 to me.)
(3) DON'T APPLY TO SAFETY SCHOOLS: If you fall in love with all of the top schools, apply. I didn't apply to any safeties, my safety was in numbers. There are so many fall back plans that are wonderful opportunities - the MAPSS program at U Chicago, working for another couple of years, etc. - that there is no reason to "settle" if you know you want to go to a top school. You must, however, be willing to do something other than school and re-apply if needed.
Those are the only nuggets of advice I can think of. This will likely be my last post as well, although you can always DM me if you think I have something specific that would be useful to you. GradCafe was very helpful to me in the application process this year, and I am more than willing to repay this favor to future generations of GC applicants!