Summarize this article in one sentence.
It may end up being cheaper to buy two one-way tickets from two different airlines instead of a round-trip package. There can also be a large price difference based on where you fly out of, so you should check flight prices departing from any major city near you. Studies show that 3pm on Tuesday is the best time to search for flights, as well as early mornings. Search for flights during these times, and also at several other times throughout the day, since ticket prices often fluctuate. There are many websites, like Kayak and AirfareWatchdog, that will monitor the prices of certain flights or destinations for you, and send an alert if the price goes below a specified range. If you have some flexibility with when you book, sign up for alerts from several websites and wait a while to see if any deals come up. Unless an airline offers a special deal, you’ll typically find the best price if you buy a ticket six weeks ahead of time. However, you should make absolutely certain that your travel documents (your passport and, if necessary, your visa) are in order before you purchase a ticket. If the price drops within 24 hours, you may be able to re-book without a fee. Once you find an affordable ticket and purchase it, check the price of that same itinerary on the same airline a few times within the next 24 hours.

Summary:
Compare prices for different airlines and cities. Check flight prices at several different times throughout the day. Join a travel website that will notify you when certain flights drop in price. Book your flight 6 weeks in advance if you don’t find a good deal earlier. Check the price of your flight again within 24 hours of booking.