For those of you with experience in list building for offline businesses (restaurants, retail stores, personal services, etc.), which method of list building seems to generate the most responsive lists? I have an email list for my cleaning business and do well with that. However, I have friends in the restaurant business that are interested in me helping them with their marketing, and I think that list building is a great way to start. We can offer things like free dessert or appetizers in exchange for an opt in, but are debating whether to gather cell numbers or emails. What has worked better for you?