Hidden Fields
Adding hidden fields to your forms is as easy as it is useful. While editing a field in your form's Build it tab, use the Field settings on the right to select Hidden under Field visibility, and that field will only be visible to you. This comes in handy for segmentation: Say you want to keep track of the different trade shows where subscribers sign up. Set up a hidden field, and input the name of the event. Then, whenever you look at a subscriber's profile in MailChimp, you'll see that they signed up at a particular event. Down the road, you could even send targeted email campaigns to subscribers based on where they signed up.
