Michele,
In a designer house, there is usually a "hostess" in each room, so that as you tour the house each room is explained to you. I also had business cards out. I didn't offer that particular designer any incentives, as I was doing her a favor as well by filling a huge space over her mantle with something interesting.
I suppose it would depend on your individual situation or relationship with a designer. Also, I had done a room myself. A friend of mine and I did a small nursery in which I painted all of the walls with cherubs, (it was quite sweet if I say so myself
) In the nursery I also had a small portrait hanging and underneath was a framed price list with more business cards. The host in that room pointed out that I was also the artist of the portrait downstairs.
About 300 of my business cards were taken, so it will be interesting to see how many calls I get now that the tour has ended. GOOD LUCK.