Sometimes you want to stay at a certain hotel only to find out it is completely booked. Wendy Parrin at Conde Nast Traveller recommends finding out the hotel's cancellation policy and snagging a room that someone else lets go.
Image from whatcouldgowrong
The trick is easy: Call the hotel directly and ask what day their cancellation penalty goes into action for the date you want to arrive. Make note of that date and call the hotel on that morning. Hopefully you'll be able to book a room that gets released by those who want to cancel their reservation without having to pay the fee. Even if you're not at the top of the waitlist, being nice to hotel staff could land you one of the newly free rooms.
A Quick Trick to Get a Room at a Sold-Out Hotel [Conde Nast Traveller]