Track them, per customer
Start by knowing who doesn't turn up. No-shows often come from a small group of the same people. Once a booking's time has passed and nobody checked in, mark it as a no-show against that customer.
After a month you'll know who to call before taking their next booking, and who to ask for payment up front.
Don't let walk-ins take a booked space
The opposite problem is a group who booked, turned up on time and found a walk-in on their court. Stop staff from starting a walk-in on a space that's booked in the next half hour, so the booked group isn't the one that loses out.
Send a reminder
A message the day before or a few hours ahead is the cheapest fix there is. A lot of no-shows are people who simply forgot. A reminder also gives them an easy way to cancel, which frees the slot while you can still sell it.
Shorten how far ahead people can book
Bookings made weeks in advance get forgotten more. If no-shows are a problem, try limiting bookings to, say, 14 days ahead, and see if the rate drops.
Take a deposit for peak slots
For your busiest hours, a deposit is the strongest tool. Keep it if they don't turn up, refund it if they cancel in time. Many venues only ask for deposits on peak slots, or only from customers with a no-show history.
Write the policy down
Whatever you decide, put it in writing: how late someone can cancel, what happens to a deposit, and how long you'll hold a court for someone running late. Staff can only enforce a policy that exists.
How playdesk handles no-shows
playdesk marks a confirmed booking as a no-show automatically once its time has passed without a check-in, and each customer's booking history shows how often it happens. Walk-ins are blocked on a space with a booking due in the next 30 minutes, and you choose how far ahead people can book. Booking reminders and deposits aren't built yet. Reminders are being built now, and deposits are on the roadmap. More on bookings.