The whole relationship with your customers in e-marketing begins with the subscription form. So bear in mind that you should create a subscription form easy to understand, short and clear.
Design: Do not put too many colors, this should simply bring your logo and the information you want to obtain. The simpler it is the more attention it will attract.
Fields: Do not make a subscription format with too many fields, ask for the most important information. If you make it very long, most subscribers will not want to fill out as much information, so at the end they will prefer not to register.
Benefits: Before your clients register information, you can explain to them what information they will receive and how often. That way your customers are clear on what they are registering for.
Remember to always put yourself in the shoes of your subscribers, not only when creating your newsletters, but also when creating your subscription forms.