In addition to ECs, it's good to do things that show your manual dexterity. There will be a question on the app. to list things like this. So if you're planning early, take something in school that will help you with this. Musical instrument (guitar is great), art classes, woodworking, or whatever you like. If you want to really wow them, learn some gang signs and throw them up during your interview. That will leave an impression they won't soon forget.