There are no difinitive answers here, other than to say most of us use the car far more often than we probably should. It is often suggested that the best way to start is to try changing your mode of travel one day a week and take it from there, but to be honest, it is often more about a change of lifestyle to create some time in your day to enjoy the journey as and when you can. After all, unless there are some clear benefits, why would you bother. Once you start to realise those benefits, you won't look back!

There are loads of legitimate reasons people give for not doing so, including time, luggage, heavy shopping, safety, weather etc. But equally, there are some really good reasons to do so; health being the most prominent, but often walking and cycling can be much quicker for shorter journeys, coaches and buses can be cheaper and rail journeys for longer trips can be the most relaxing trip you've had in ages (and cheap if you plan ahead).

One of the great inventions of the modern age has to be aviation, second only perhaps to the internet for opening up the world. 

But it is also likely to be the biggest single ticket item on your carbon footprint, with a long-haul flight emmiting up to a tonne of carbon per passenger per flight. For frequent flyers, this can easily double or even triple your emmmissions for the year. 

The converse of this means that reducing the number of flights has a correspnding significant benefit, and may well be the 'easiest' smart choice you can make.