Biking with the kids is one of our obvious changes to working towards an eco-friendlier lifestyle. As 350 Sacramento says, find one thing you can do to make a difference and do it. Maybe you can bike to work a little more often, take your own shopping bags to the store, carry a reusable bottle instead of buying plastic. You don't have to swear off warm showers but maybe you can buy your veggies at the local farmer's market. You don't have to sell your car (that's crazy talk) but maybe you can find an alternative mode of transportation for most trips under 2 miles.
These are my reasons for doing the things I do to make a difference.