Finding the best price for an airline ticket is the real journey of the fighter. Here are some tips we use to find our cheap flight tickets:

To find the right price, you have to compare! For our part, we mainly use the Skyscanner comparator (because it integrates most of the low-cost European companies). But others are also very good job like Momondo (it is interesting to test your research on Momondo because we sometimes find even cheaper flights on Skyscanner) or Google Fligth to name a few.
A departure of a few days can significantly reduce the price of the plane ticket. All good comparators offer a flexible date option.
Leaving on a Sunday or mid-week can usually find more interesting prices.
Flights early in the morning or late at night are also often cheaper.
For domestic flights, for example in South East Asia, use a local flight comparator because European flight comparators do not include local low-cost airlines. For example in Asia, Air-Asia offers low-cost flights unbeatable.