Finding cheap flights always requires a little bit of luck, but it's also somewhat of an art form. Sure, you can stumble upon cheap airfare by accident when you're booking a trip, but you'll have a much better chance at lower prices if you know where to look. The following tips can help you save big no matter where you're traveling next.Use Google Flights to Compare PricesGoogle Flights, a free tool anyone can access online, offers one of the easiest ways to compare prices among multiple airlines. This website lets you evaluate fares for round-trip, one-way and multi-city tickets for nearly any destination around the globe. After inputting your origin and intended destination, you can use the calendar to see prices by day in one place. This feature makes it easy to quickly compare fares and travel dates, and can save you from performing multiple searches to see how prices stack up from one day to the next.If you're flexible on where you want to go, you can also compare flight prices from your home airport to various regions of the world. If you want to travel to Europe or the Caribbean, for example, you can search either region in Google Flights to find a destination where you can snag the best deal with your dates.[See: 50 Cheap Tropical Vacations to Take This Year.]Note, however, that you cannot book your trip using Google Flights. The website shows you the best priced and best value flight options for your destination and dates, but you'll have to book your flights directly with the airline itself or through an online travel agency like Expedia.com or Priceline.com.Check SkyscannerSkyscanner.com is another online tool that lets you compare prices on airfare and find out about airfare deals to destinations you may have never considered. Its search "everywhere" feature even allows you to look for flights from your home airport to anywhere on the globe. All you have to do is pick an airport, select your dates and list how many people are flying to find out the best airfare deals available. You can also use Skyscanner to set up price alerts that inform you every time the price of a flight you want drops by a certain amount. Be Flexible with Your Destination and Dates This brings us to the next important tip – make sure you have some flexibility when it comes to your destination and dates. Having to travel to a specific place on a very specific timeline is the death knell for any travel budget, whereas being open to multiple destinations and a handful of dates makes it easier to compare options and score a deal.Imagine you're searching for flight deals and you're willing to travel anywhere in Europe, for example. Or, say you know you want to go somewhere warm but you're open to considering the Caribbean, southern Florida or even Hawaii. In either case, you could compare prices for each vacation spot using a tool like Google Flights or Skyscanner.com and book whichever deal is best.The same flexibility with dates can also help you save money since flight prices tend to vary from one day to the next. If you're able to fly Monday to Monday instead of Saturday to Saturday, for example, you could pay less for your fare.Travel Off-PeakSpeaking of Monday to Monday trips, having the ability to fly during the week can often help you save some cash no matter where you're traveling. While this isn't always the case, it's common to find lower prices for round-trip airfare on Mondays, Tuesdays and Wednesdays when comparing to itineraries flying on Saturdays and Sundays. Of course, you'll want to play around with Google Flights or an airfare search engine to be sure. Traveling during the offseason can also help you save money depending on where you're planning a vacation. By and large, you can find affordable flights if you avoid booking travel during school breaks or during a destination's peak season. It can be pricey to visit the Caribbean, Mexico or Hawaii during winter months, for example, yet prices tend to drop dramatically during warm summer months in the U.S. [Read: The Best Affordable Family Vacations.]Start Researching and Planning EarlyAccording to a study on airfare prices conducted by CheapAir.com, the best time to book airfare is between 21 and 175 days in advance. That's quite a span of time to pay attention to prices, and it goes to show just how unpredictable fares can be in the first place. So, how can you know when to book if the best pricing could be today or months from now? Your best bet is starting the research early so you have a baseline to compare pricing as the weeks tick on.By starting your search early, you can use a flight search tool to tweak travel dates or destinations until you find pricing you're comfortable with. If you need a little help, you can also download the Hopper app and set up a fare alert. Hopper says it can predict airfare pricing with 95 percent accuracy up to a year in advance, so the app can be a handy tool to add to your arsenal.Whether you opt to shop around yourself from time to time or set up a fare alert, you need to be ready to book once the price of the flight you want is within reach. If you put the purchase off and forget, you may wind up paying a lot more than you planned. Wait for a SaleAirlines tend to offer periodic sales that can seemingly come out of nowhere. This can be frustrating if you don't keep your finger on the pulse of the latest sales, but it's the exact reason those who pay attention tend to save the most. While deals aren't always advertised, one of the best ways to find out about airfare sales is by signing up for email alerts from your favorite airline or airlines. You can also follow airlines and travel blogs on social media to hear about special sales and discounts. Additionally, websites like TheFlightDeal.com and SecretFlying.com can be excellent resources when it comes to discovering inexpensive international and domestic airfare deals. Both websites post an array of airfare sales that change on a daily basis. Although, you have to be ready to book since the majority of deals last a few days at most.[See: The 50 Most Beautiful Landscapes on Earth.]Pick Up an Airline Credit Card (or a Flexible Travel Credit Card)If you don't fly often enough to rack up many airline miles, you may want to consider picking up a co-branded airline credit card or flexible travel credit card. Either option will let you earn miles you can use to book flights around the globe.With the Chase Sapphire Preferred card, for example, you'll earn 50,000 Chase Ultimate Rewards points after you spend $4,000 within three months of opening an account. Those points are worth $625 in travel if you book airfare through the Chase Ultimate Rewards portal, but you can also transfer them 1-to-1 to popular airline rewards programs like United MileagePlus, Southwest Rapid Rewards and JetBlue TrueBlue, to name a few. To put things in perspective, 50,000 miles may be enough for two round-trip domestic flights on Southwest and it's often enough for a round-trip flight to Europe with the Air France Flying Blue program. Keep in mind, however, that the Chase Sapphire Preferred charges a $95 annual fee after the first year. You could also pick up a card that is specific to an airline, such as the Citi AAdvantage Platinum Select World Mastercard. This card offers 40,000 American Airlines AAdvantage miles after you spend $2,000 within three months and 10,000 additional miles if you spend a total of $6,000 in purchases within the first 12 months of opening the account. With 50,000 miles in your account, you can book two round-trip domestic flights for only $5.60 per leg – the cost of government-mandated taxes and fees.While pursuing airline miles requires some strategic planning early in the process, it doesn't get much cheaper than that.