Firstly, don’t fly. All the good you do in the home or daily travel is absolutely dwarfed by carbon emissions from a single flight. Read up about holidays that don’t involve flying and try and convince whoever you normally holiday with that these are better holidays. Wherever you live, look up the best train journeys, (Deutsche Bahn for Europe) bus journeys, cycling journeys, or ferries, and aim to travel and experience, not just fly. Visit The Man in Seat Sixty-One for further guidance on planeless travel around the world.
However, if not flying is not possible, then try to…
- Book well in advance, so you have something planned to look forward to. Spreading out the trips that involve a plane will reduce the number of flights over a lifetime. Fly less and stay longer. For the rest of the time, go on short weekend trips near by instead.
- Avoid luxury seating. These are responsible for 40-50% more emissions than standard class.
- Pack light. Keep in mind the carbon footprint of flying mangetout peas around the world, and think about it while you pack. Do I really need to take a full bottle of shampoo? Coordinate packing with your co-travellers so you can share essentials whilst away and take only as much as you need.
- Favour daytime and summertime flying. The contrails that appear behind airplanes have been found to produce a cooling effect for the planet by reflecting sunlight back out to space when they are newly formed, but as the contrails spread out, this phenomenon is replaced by a blanket-like effect that traps the earths heat in. So in balance, if you are going to produce the contrails anyway, try and make sure they are reflecting sunlight back out to space to offset some of the overall warming. So flying at night or in winter are the worst times to fly for climate change impacts and have double the climate impact than summertime, daytime flights. See the article here in Nature magazine.
- Use public transport to get to the airport. It is the least you can do. Sprawling car parks around airports are your fault if you drive, and every airport will have provided for public transport.
- Consider offsetting, but don’t begin thinking this makes up for frequent flying. See Choose climate website for a calculation for carbon emissions from flying.
Some great guidance can be found at Aviation Environment Federation for reducing the environmental impact of flying.
decarbonate 
I have found that raising the issue of carbon emissions from flying is the single most controversial topic during climate change discussions with friends!
True. It is an extremely emotive subject. There is a concept that one ‘green’ action means you can do more of another ‘non-green’ action… I always recycle, so I can have a holiday from it and fly to somewhere sunny.
Yes and it sometimes goes further than that as in ‘I do my bit by always recycling….’ which implies there is no need for me to do anything else!