Start with these ten steps – from The Big Melt.

1. Reduce energy usage: insulate, drive less, use hybrids & electric vehicles, unplug
2. Switch electricity supplier to 100% solar or wind
3. Buy sustainable products to incentivize businesses to make more of them
4. Plant native trees and shrubs to clean our air & water and cool things down
5. Support local and national environmental non-profits
6. Reduce meat consumption and food waste
7. Encourage businesses and governments to support solar and wind energy development
8. Encourage energy-efficiency upgrades in all buildings and vehicles
9. Support the expansion of interconnected green infrastructure networks
10. Implement a national “carbon cap and dividend” policy or a “carbon tax” to pay for the real and hidden costs to society of using dirty fuels

For more ideas see Drawdown by Paul Hawkens.