There are many ways to earn playing time. The most important one is to be worthy of that little extra time the coach gives you. Show the coach that you are only here to help your team and that you will spend each second of that playing time in a helpful way. Do what you are good at during that time so that your coach can acknowledge your efforts and think of giving you extra moments to play. Be a worthy player and be tactful so you can earn extra playing time from your coach.