Go car-free. Walk or ride a bicycle (unless it's dangerous). You can also take public transportation (if available).
Avoid air travel. In particular, avoid short-haul flights and take the train instead. If you absolutely need to take a plane, fly in economy class only. Don't even think about first class or business class.
Go to the local grocery store by foot and put the items you purchase in your own shopping cart.
Consider video conferencing instead of travel.