In your effort to stay in touch, add value, and generate referrals, you want to pick up the phone and call some of your contacts weekly, some monthly, and maybe some only one time each year. If you don’t reach them, leave a message so they have a record that you called them. To organize the effort, create phone lists that are segmented by the level of connection and frequency of contact you have with each group.
Don’t hesitate to pick up the phone and make calls just to thank people for their business, see how they’re doing, and ask if you can do anything for them.