Check alternate airports
If there is more than one airport near your origin or final destination, check them both before making your flight booking.
The more options you have in terms of airports and travel dates, the more likely you will be able to find the best deals on airfare.
And consider multi-city flights as a strategy to save money.
Ensure you know where the airport is situated in relation to your accommodation and before you book your tickets. We messed up once and discovered I was flying into an airport much further away from the city centre. It cost me extra to pay for a bus into the city centre and a lot more in time than simply flying direct to the main airport.