It is always best to check for airfare with as much advance notice as possible.
Occasionally you do need airfare at the last minute and when this occurs, there are several options you have to ensure you are getting the best deal possible.

When you need to find a last minute airfare, you can contact the airline to determine if they have any cancelled reservations. On occasion, the airline will lower the price of the airfare when they have cancellations in order to make sure the flight is full.
When you purchase a flight this way, you may have to accommodate your own schedule to take advantage of the flight sale, but if you're trying to save money, this is an excellent option.

If you have the luxury of being able to plan your vacation, you can take advantage of airfares by booking in advance. Most airlines offer the best prices to travelers who make their plans several weeks in advance. If you plan your flight in advance, you can receive optimal pricing and in many cases, you'll have first choice at seating on the flights.

If your vacation time is flexible, you may also want to consider searching for airfare with flexible dates. Airlines often offer better pricing on dates that vary a bit from what you were considering. Airlines may also offer better pricing on days in which they have fewer business travelers as an incentive to fill empty airplanes.

They may also offer discounted fares to travelers who are willing to travel late at night or early in the morning, known as "red eye flights".
Regardless of your situation, time frame and destination, always take time to review your travel options and price several airlines before booking your flight.
By checking various dates and airlines, you will be able to find the cheapest flight.
In addition to reviewing pricing, you may also want to consider the flight times and layovers before you book your flight.
You may be able to save some money by having a layover, but if time or timing is a consideration, you may have to spend the extra cash to book a flight that meets your needs.

Years ago, travelers contacted airlines directly to make their flight arrangements or contacted a travel agent.
Now, there are many different travel web sites in which to search for flights. The top web sites will allow you to search for flights with various options including price, date flexibility, and nearby airports.
You should review pricing on several online web sites before booking your flight. There are even web sites which allow you to "bid" on the price you're willing to pay for a particular flight.

If the airline wants to fill the flight, they may accept your bid, saving you quite a bit of money.

When reviewing your flight options, you may also want to consider booking a hotel and/or car rental in conjunction with your flights. Many airlines, hotels, and car rental agencies offer a discount for booking these services together. Regardless of your situation, if you take the time to review flight and airline options, you will be able to save some money and enjoy your vacation with a few extra dollars in your pocket.