. They ask, if I remember correctly, for 12 hours advance notice. They also offer a shared shuttle service which will stop at several hotels for $15 per person.[/QUOTE]

The one I used was Prague Airport Transfers: www.prague-airport-transfers.co.uk

550 CZK private car or 290 CZK for the shared shuttle. I got a Mercedes SUV on the shuttle ride into town and a nice VW on the private trip to the airport. You can book online or by phone and they operate 24/7. With the private car to the airport I just told them when I wanted to be picked up, so it is completely within your discretion.