Acknowledge that cats are sociable animals to a point, but not sociable to the extent that dogs are. A lot of people who have one cat decide they would like to have another cat, thinking two cats are twice as much fun. But the cats may not see it that way.
The simple message I would like to get across is if you do want to have more than one cat, go about it in a careful way—and be prepared to give up on it if it doesn’t work.