What I have done to reduce my negative impact on the planet:
Vegetarian since teens
Drive fewer than 4K miles a year (true over the last
10 years, and as an average over my adulthood)
Cycle more miles than I drive
Compact florescents, rechargeable batteries
Use 2000 kWh a year over the last four years (and my
house has no other energy source)
Don't have a lawn (don't use pesticides or fuel,
promote eco-diversity)
Spend less than $7K a year (consume and produce less
garbage than the average American)
Don't have children