Align yourself with great people. When you want to change the world, you will need a team. The best way I have found is to align yourself with great people who are already doing the work. Find an association, foundation, not-for-profit, or agency that is already working in the area that you care about.
Are you concerned about housing disparity? Serve on the citizen's advisory board for your city's housing or development committee.
Would you like to see greater racial justice? Attend a march, listen to the speakers, give money to an advocacy organization.
Care about conservation and the environment? Pay the dues to join a not-for-profit, read their publications, make a donation.
“Never doubt that a small group of thoughtful, committed, citizens can change the world. Indeed, it is the only thing that ever has.” -Margaret Mead