Got a credit card? Use it.
Some credit card companies offer air miles programs on their cards. Check if yours is affiliated with an airline company. You can take advantage of these offerings in case you need to travel pronto. Plus, you might even collect rewards points as well.
Check if it's that time of the year.
Airfare and hotel prices fluctuate, depending on the season. If you want cheap last minute travel deals, go off season when there are fewer travelers and companies are raring to fill their seats and rooms. You could get a great discount if you only choose to travel when business is slow.
Many travel agencies purchase multiple flights and use them to promote package tours. In case your destination is included in these bundles, consider buying a seat. Although most of these trips sell fast, you could find cheap last minute travel with these agencies. This usually happens as the date of departure approaches. If there are packages that have remained unsold, you can be sure that they will be sold at highly discounted prices.
The advantage here is that you not only get to cover the airfare, you also get accommodation (and probably breakfast) thrown in. All in all, that should be way less than the cost of a regular flight and hotel booking.
Sign up for e-mail alerts.
Many airlines and hotels send out alerts regarding great deals on their products. You could take advantage of these in case you need to travel last minute cheaply. Check your e-mail boxes regularly if there's a good deal currently active around the time you have to travel. Just be careful, though.
If you go this route, make sure you really are going to travel. Most of these companies offer these deals as non-refundables.