Include a signup link in your email signature
If you’re using a professional email marketing system like Constant Contact, you can generate a link for your email signature that allows people to sign up for your mailing list. Every time you send an email you have an opportunity to build your mailing list.
Add a signup box to your website
Again, because you’re using a professional email marketing system (right?), you can generate a form that can be added to your website. Use the link you generated for your email signature. Make sure the link is prominent on your home page and on your contact page.
Wherever you’re meeting people, carry business cards. Whether you’re at a networking event, trade show or a baptism and you exchange cards, ask if you can add that person to your mailing list. After a little small talk of course, and you’ll find that most people are happy to join your list!