Make the right car purchase
Choose a car with a low impact on the environment. Think carefully about which car you really need and for what purposes you're going to use it. The EU energy label is a compulsory and useful indicator when choosing a new car. This label indicates the CO2 emissions and the fuel consumption.
Some sites offer a more detailed list concerning the environmental score of vehicles.
You should also consider alternative transport such as car sharing, public transport, etc.