What's the best route to take after undergrad if you want to end up with a PhD in I/O?

Obligatory background: I just finished my junior year of college, and let's say my grades are definitely competitive in relation to other potential doctoral students. I will have had three years of research experience by the time I'm done with school, as well as an honors thesis that may (or, more likely, may not) be published. I have not taken or studied for the GRE yet.

I'm wondering what a person like me might do to really shine as an applicant to a doctoral program in I/O. Should I try to work for a company and get actual "organizational" experience? Should I try for a position doing research for something related to business or I/O rather than the clinical/psychiatry/neuroscience stuff I'm currently doing? I'm assuming that I can't apply right out of college because that would require getting the GRE stuff together pretty quickly.

Any advice and/or shared experiences would be incredibly helpful.