Following Harold’s excellent example, I have put everything you need to know to be an environmentally responsible citizen on a 4×6 card. (I wish environmental policy could be similarly condensed, but it’s complicated; “Carbon charge!” goes a long way, though.)
Walk, bike, e-communicate, and public transit when you can. Drive a high-mpg car, and keep it as long as possible.
Live close to work and shopping
Eat less meat.
Garden appropriately for your climate. Less turf.
Drink tap water, not bottled. Showers, not baths.
Insulate, weatherstrip, switch to CFL and (better) LED light bulbs. Then, focus on (i) in winter, energy that goes out through the walls of your house: lower the thermostat and put on a sweater, don’t obsess about lights and appliances because they just offset your heating system; (ii) in summer, what comes in and has to be taken out by air conditioning: shades, awnings, whole-house fan; raise the thermostat and wear shorts; turn off lights and minimize cooking and appliance use.
Reuse, repair, retain; have less stuff and less house (share walls, consider an apartment), but have a recent refrigerator, and a dishwasher that you load full before running.
Vote and agitate. For a carbon charge, walkable/bikeable/transit land use, high gasoline taxes and low fares; against free parking.