Where do you buy tickets

Where do you buy cheap tickets when you have to go somewhere abroad? And do you prefer traveling by plane or train?

When I want to go somewhere abroad, I buy tickets only online, because it helps to save money on time. And every time I use this site https://europefly.com/en, becuase there are the vest prices in every destination. What I like the most is the interface, it helps to do everything effortless and fast.
P.S. Yesterday I bought plane tickets to Italy, and the price was reasonable even during the Chrismas period!