Try to minimize the number of flights you take by combining trips. For example, book more than one meeting in your destination city, so you don't need to fly there several times.
Fly during the daytime, because studies have shown that flights taken at night have a greater impact on the climate.
Fly economy, because more people per plane means fewer emissions per person.
Pack light, because lighter planes mean less fuel is burned.
Purchase carbon offsets to account for the emissions from your flight.