Don't worry about joining many clubs. A few clubs that you are more deeply involved with is better. For example, try to go to as many meetings as possible for your environmental club. Then apply for an officer position at the end of the year.
Boy's State (and Girls State) is sponsored by your states American Legion. It teaches leadership skills and how your state government works.
Here is the link for more information:
From what I can see, all the applications for college and service academies ask if you have attended Boy's State. I know that I took the time to go and it was definitely worth it.