Join the Green Party
The Greens are a powerful fusion of movement and political party, melding and building on the strengths of the peace, social justice and environmental movements and giving them all an electoral voice. In California, a voter registration form allows you to formally register green - just pick one up at any government building (the post office will probably be closest to you), fill it out and mail it in.
However if you want to join the Green movement, the best way is to join a local green chapter. If you're in the Long Beach, CA area, start by signing up for the Long Beach Greens listserve (click here and send our listserve a join request) or coming to a monthly meeting.