Let them have space to walk around, look at it all alone and in depth, don't rush them, let them know you are happy to answer any questions and then give them the time to see themselves in it and talk honestly about what they value/don't.
When I view for the second time what I really want is a heart to heart with the owner about what they perceive to be a realistic price. Hard to do I know, and harder with the agent present but I have left a few houses knowing that if the sellers had been prepared to talk money there and then I may well have bitten the bullet, doorkey, cherry.
Other than that it is a lack of time to view that I hate. I had one estate agent show me a house and the moment we walked through the door she looked at her watch and asked me how long I would be.