This is not as easy as it should be.
photo credit: TheSeafarer
If the contact is not already a friend, there seems to be no simple way to add him/her as a fan. You could pay for advertising, but most small businesses are trying to get wider coverage using social media and are trying at the same time to avoid increasing their marketing expenditures.
There is a distinct push by some consultants to have small businesses build their web presence using Facebook fan pages as opposed to building a traditional web site., It would be interesting to find out how they get their customers to add fans without them having to first belong to the friends list.
If you know the answer, please leave a comment.