FSOT and GRE

So people who belong to the Future Peace Corps Volunteer Group Page on Facebook, often talk about FSOT. So today I was curious. FSOT stands for Foreign Service Officer Test. I did research and it sounds interesting. The career track which I would want to pursue would be a "Consular Officer". Here is a website with more information: http://www.careers.state.gov/officer/selection-process. I haven't decided anything and I probably won't however doing research on what could be my future is fun. I also did research on the GRE test. I haven't taken it yet, but I'm trying to decide if I should take it before leaving for my service, while serving or when I return. Researching seems to be my best bet as of right now, looking at the various options I have.