Send a little Light everyday. Just for a few moments, before you go to sleep and/or when you first get up, put your hands over your heart chakra, close your eyes, and visualize Light. Then, visualize sending it to the darkest corners of the world.
Don't send it where there's already an abundance of Light, but to places where darkness appears to have taken over. Send it to the Middle East. Or to the Oval Office. Or to Congress. Or to the greediest of Corporations. Send it to terrorist cells. Send it to people in your life who have treated you unkindly. Send it to where people are dying, and where human rights don't seem to matter. Send it to fascist dictators and to war-torn and poverty-ridden regions.
Beam that Light to places where darkness appears to live, because you can't fight darkness with more darkness. You can only combat it by turning on the Light.
And as you visualize, affirm. Affirm that the Light you are sending will bring peace. That it will bring prosperity. That it will bring wisdom and compassion. That it will bring Love. That it will bring wise and compassionate leadership. That it will bring healing and joy. If enough people make this tiny effort every day, eventually even the darkest places on earth will be filled with the essence of who we truly are - Light.