One of the biggest influencing factors of airline tickets is the time of year. If it is near a holiday season the price will be more costly compared to the off-season airline tickets. For example airline ticket prices right before Christmas will be more expensive compared to a month or two before Christmas.
Size of the airport will usually affect the price of the airline tickets as well. If you want a cheap airline ticket it is always advisable to make your departure from a large international airport if possible. If your destination airport is in another country, then the flight will be considered as an international flight. Try to purchase an airline ticket that has minimum layover. The more layovers means higher ticket prices. Some airlines, although rare, will charge less for flights that have several stopovers. It is not unusual to find red eye flights with huge discounts.
If possible, avoid purchasing airline tickets over the phone, most airlines will charge a big fee for purchasing over the telephone. There is even software that will help you find the cheapest tickets. If possible never purchase an airline ticket from a travel agent. If possible purchase your airline ticket ahead of time. Generally the cheapest tickets can be found from Monday to Thursday. If you are a student then many airlines offer discounted airfare on student travel. If possible try and book a plane ticket with an airline that offers frequent flyer miles. A great source for cheap airline tickets that often gets overlooked is the online auction site. If you purchase in advance you may even get a good price on a plane ticket with an airline that normally would cost a lot more than a low cost or no frills carrier. It is not unusual to see good prices even for business class tickets either.