Periodically send updates, tips, facts and stories to your client list. Make sure you don't abuse E-mail. Don't spam people, probably once a month is fine. I make one pile to open and the ones with mailing labels usually go unopened into the trash. Hand address or use laser printers on your envelopes.
Colorful stamps get attention and usually get opened.
Talk to your competitors and your competitor's customers. Pizza Hut didn't begin delivering pizzas until Dominoes arrived on the scene. Look at other industries and find out what they do that you can apply to your business. Don't get tunnel vision and only look at similar businesses. Be Different -Americans love trends and the zany.