Any student can show initiative. You don't need a high GPA. You don't need perfect test scores. You don't need to be the president of the club or the captain of the team or the lead in the school play. And the best thing about initiative is that you don't have to wait for someone in power to give it to you. That's why they call it "taking initiative."
If you look at the applications of successful college applicants, you'll see initiative all over the place–students who didn't wait to be invited to make things happen in or out of class, who instead just took those opportunities on their own. Colleges know it's those students, the ones who took the initiative to make an impact in whatever they got involved in, who are going to keep making that impact once they get to college.
Whether it's asking a teacher for help, contributing to the class discussion, running the fundraiser for your club, offering to help organize an event where you volunteer, or just voicing an idea you have and want to try–don't wait to be asked to make a difference. Take the initiative now.