1. Opt-In Forms: Place opt-in forms on your website, blog, or social media platforms. Ensure that these forms are easy to find and fill out. 2. Gated Content: Offer valuable content like eBooks, whitepapers, or exclusive reports in exchange for email addresses. 3. Webinars and Events: Collect emails during sign-ups for webinars or events. 4. Referral Programs: Encourage your existing subscribers to refer friends in exchange for incentives.