Agree with above. However, IF you expect to have the same MOCs come Inauguration Day, you can get a head start on what they will want by checking out their websites for their current nom applications.
A couple of caveats -- even a sitting MOC can change the "requirements" for a nom (i.e., different essays, different forms), so what the MOC requires this year may differ a bit next year. Still, MOC nom packets for the same MOC typically don't change much year to year. Second, for many of you, some or all of your current MOCs may change due to their voluntarily leaving Congress or being defeated. In that case, you'll have to deal with whatever the new MOC(s) requires and that info probably won't be posted until sometime in the spring.
Start working through the USNA and Congressional websites as well as this website and develop a candidate calendar of your own. There are many way points to hit on your course to an appointment. The nominations you are eligible for (at least four), essays, extra-curricular activities, your junior year grades (the most important in your candidate package), recommendation cultivations, they are all important to chart out at this point. As one of the first way points, I would also keep the Naval Academy Summer Seminar (NASS) on your radar. Applications for this great program open in February 2009. You would attend the summer between your Junior/Senior year.