Keep your dates flexible. Many airlines have specific requirements for a minimum and maximum total number of days to be spent in a location in order to get the best deal. For the cheapest flights, stay for a minimum of 2 nights and a maximum of 30. Try to stay at your destination over a weekend, as flights that bookend a Saturday night are cheaper than those that lack a Saturday stay.
some type of promotion.
advantage that websites may not have.
You're not crazy for thinking that a flight price has changed after searching it a few times in your web browser. Based on the cookies in your browser, flight prices do increase when a particular route is repeatedly searched, as the site wants to scare you into booking the flight quickly before prices get even higher. Always search for flights in incognito or private browsing mode to see the lowest prices.