When it comes to extracurricular activities, they look for the rounded student, example you could be apart of an AV group or robotics group but so many other students as well; playing sports, doing tons of extra volunteer hours, being apart of a social group, and joining government groups all help play a vital roll, they would see your smart and your willing to go above what is needed. Everything helps you out, more you have under your belt the more you will stand out.
Great things to join is
Track and Field, Cross Country, Student Government, International Studies, Honor Societies, Soccer