I read a blog about calling old customers. Calling old customers should be fun for us. It shouldn't be a chore. Did you have their best interests at heart when you sold them their home? Did you like the clients as people?
Over the years some of my clients have been good friends. I try to go the extra mile, and not to let them feel it is just about a sale. You want to get a client to be a friend, and you want to be a go to person. A person that they really trust. A trusted friend is what you want to be.
It's about giving more than taking. Do you send them information they can use? Do you do something for them after the sale? It doesn't have to be every year. But you need to give back. Giving to your clients will bring you big rewards. Then it becomes a way of life for you. Helping more than taking becomes your characteristic.
So the bottom line is calling an old customer shouldn't be a business goal. It should be a personal goal. It will come natural to ask about kids, the house, and their life. Then saying "if you know of anybody looking to buy or sell a house please give out my name" won't be a hard thing to do. And making the call should be really simple.