Bear in mind that if you are going to a hotel, you can phone them and they'll send a car round straight away. It's more expensive, but more dependable!
Also get a card from the hotel drivers, as they usually work for a seperate transport company. Again, more expensive but at least you can get a car at short notice. The drivers are a lot more pleasant too :)

"Never argue with idiots. They'll drag you down to their level, then beat you with experience."