Twitter has Twitter Lead Gen Cards, which let you generate leads directly within a tweet without having to leave the site. A user's name, email address, and Twitter username are automatically pulled into the card, and all they have to do is click "Submit" to become a lead. (Hint for HubSpot users: You can connect Twitter Lead Gen Cards to your HubSpot Forms. Learn how to do that here).
When a subscriber is sorted into a segment, it can trigger an automation to send to them. Each person’s interactions with your email campaigns or your website can trigger a sequence of follow-up emails based on their interests, allowing you to hone your message to your targeted audience. For example, if someone visits your pricing page, you know they’re probably further down your sales funnel and will want to follow-up appropriately. Or if they went to a specific product page or clicked on a link for that product, you can send additional information about the product, testimonials and more.