How can we be better customers at the checkout?

After reading the Packing bench thread, it got me wondering - how can we be better customers, particularly at the checkout?

Reading through the thread it seems that a lot of people don't realise that checkout staff are judged on the speed of the transaction (from first item scanned to payment etc).

I try to help by:

• Having my card out and ready before my items are being scanned
• Throwing everything into a bag as quickly as possible and sort it out later

But are there other things customers can do to make it easier/better for cashiers as well as themselves?