No one makes money running an airline. Which is great for consumers, as the market is competitive enough to make profits razor-thin. So don’t stress about getting a cheap flight. Flights are already cheap. Buy early. Waiting for a cheaper flight sometimes works, but it’s a hassle and a gamble.
In general, booking four to six months ahead or so is enough. Amazing deals tend to be flukes, and only work with a flexible schedule. I went to Ireland from Ohio for under $300 thanks to a mistake fare, but only because I was online within a three-hour window and my boss gave me the time off.
Rick Steves has an overview of budget flights within Europe. Some websites such as Airfarewatchdog and The Flight Deal post deals and error fares; follow them on Twitter and Facebook. Those deals rarely last more than a few days, sometimes a few hours, so waffling is discouraged.
Dozens of flight search engines exist, and all of them differ. If the desired flight is within the United States, for instance, Southwest won’t show up on most engines. Go to their website and search directly. Use different search engines until one emerges as the most useful; the best engines for tickets from Ohio to Europe probably aren’t the best for tickets from Oregon to Asia.
Tickets can’t be bought through ITA Matrix, but it’s the best engine for complicated searches and to find the best prices. The Flight Deal wrote a beginner’s guide for it last year. It’s great for finding a flight to purchase elsewhere.
Skyscanner is my default. It’s simple with good results, but it’s not the best to compare multiple dates or destinations.
Occasionally, it beats Skyscanner, and it’s easy to compare multiple dates and destinations, as well as finding open-jawed tickets.
A less-useful Hipmunk for me, but worth using for comparison.
Their Price Trend tool (with a confidence level!) is great; it advises whether to buy now or wait for a price drop, but otherwise, I never bother with Kayak.
Don’t fret over flights. Summer flights will always be more expensive than any other time. Except maybe Christmas. It can be cheaper to fly into one city and take a budget airline to the final destination instead of direct, so look into that. London, Istanbul, or Amsterdam can be good for that, among others. Experiment.