Buying a last minute flight is actually quite tricky. Many charter airlines will deal primarily with packages and as such the flight-only option can actually end up costing more than a simple package.
All is not lost though! There are still plenty of ways to pick up a flight bargain. Bear in mind that if you are going for a do it yourself option on your holiday, it is wise to book the flight first, as this is likely to be the largest expenditure and there is generally less of a variety of carriers meaning less room for negotiation. Almost without exception finding a cheap hotel will be easier than finding a cheap flight.
Trawl the websites of those flight operators that cover the location which you wish to travel to. Join their mailing list. OK, so you may end up with endless junk mail, but you will also get to hear about all of the deals that they are currently offering.
As a general rule, the best deals are available for flights leaving Monday to Thursday and on domestic flights many bargains can be found on a Saturday. Travelers will almost invariably pay more for a Friday or Sunday flight. Most holiday operators will offer the best deals for those who purchase a set time in advance, normally at least 14 days. If it is possible to stay a Saturday night, this will also normally result in a lower fare.
When searching, if possible, entertain the possibility of a flight that involves a connection. Airlines often place a large premium on non-stop flights and if this is not vital for you, you are likely to be able to save many dollars.