5. Use Priceline, especially if you don't have a sufficient advance purchase window. The cheapest fares often require a 7, 14, 21, or even a 28-day advance purchase. What if you need to leave tomorrow or on short notice?  That's where Priceline's "Name your own price" bidding process can help. Typically, savings reach 40-60%, sometimes more.  The site has added a page showing a daily list of discounts on the top 50 routes, revealing how much other users have saved by bidding on fares.

Click on the route and you'll see actual bids vs. the lowest retail price

See tip 6.