For old customers, you have to understand he had ordered products in your company, ask him to buy your products, how to pull. Or talk about your new products, or sometimes can talk about everyday matters.
For an old customer, you must understand him before you order products, ask him, buy your product what pull. Talk about your company or new products, or sometimes can often talk about.
For regular customers, you get to know him before in your company ordering products, ask him, how about buying your products. Or tell us something about your company's new product, or sometimes to talk to home cooking.