What are the most legitimate and frugal ways I can go about buying a plane ticket?

I'm trying to get a one way ticket to Sacramento California from Cincinnati Ohio. This is my first time ever buying a plane ticket and I really want to get the best price possible. How should I go about this? What are the most reliable websites? Anything else that would help the cost? I only need a one way for 1 adult and all I will be bringing is a duffle bag of clothes.