<p>EC - you mean like extra-curriculars? Virtually irrelevant. </p>
<p>The most important “extra” thing you can do is get involved in research relevant to your field. Other than, get excellent grades, get to know three or more professors pretty well (you’ll need them to write LORs for you). Fall of your junior is not too soon to begin work on your statement of purpose. Begin to practice for the GRE about then (if your field requires it).</p>
<p>That covers what will be important: GPA, research and recs, SOP, and GRE, pretty much in that order.</p>
<p>Also, keep in mind that the Ivies are VERY small universities. Many departments have graduate classes of 4 or 5 students in any given year and will be getting 100 or more applications for those spots.</p>