In order to obtain new customers it is important that you expose the subscription form that we provide you in your website. If you do not have a website, it is important that you gather information from new clients, you can have a printed sheet and have your clients fill out their information for you to send them tips on the industry, or send them offers, but also letting they know they are signing up to your list to receive newsletters from you.
In order to keep your current subscribers, and change their minds if they ever think about unsubscribing, you must be consistent with them, and send them a recurrent newsletter with the same frequency, either every week, every month, ever 2 weeks. Also, make sure to send an auto reply to your customers after they sign up, so they keep in their minds that they opted in to your list. And last but not least, make sure you get to know your client. Classify them, by different interests and send them only what they would like to receive. Do not over send them information that will make them unsubscribe from your list.